I owned the ‘Italian’ SM300 illustrated in Pic 18 for a short while and whilst carrying out some research on this watch came across an interesting posting on a French website.

For this ‘Quick Guide’ I started with the French posting as a base and adapted it with some very extensive additions, editing and rewriting plus changing and/or adding pics and it is designed to assist the collector in search of a Seamaster 300.

As there are many sites that cover all aspects of a SM300 such as new builds, fakes and bracelet adjustment etc. in some depth I have not included these topics.

I am certainly not an expert so am unable to verify that all the information contained is 100% correct. Given that some of these watches are over 50 years old it is very difficult for any guide of his type to be totally accurate.

I welcome your views and comments especially if you have further information or believe there are inaccuracies. But please don’t shoot the messenger!

Wherever possible the copyright for the pics has been acknowledged.

 

PIC.1 – Courtesy of gemini4 (Omega Forums)

Although the Omega Vintage website states the SM300 was in their International Collection from 1962 – 1969 it probably did not reach the dealers until 1964. It was available either with a metal bracelet or leather strap.

Initially the SM300 was available as non date watch with a centre sweep second hand. The majority of non US watches used an Omega cal.552 movement with 24 jewels created in 1958. The Omega cal.550 movement with 17 jewels created in 1960 was chosen specifically for the American market, as watches that exceeded 17 jewels were subject to more tax in the US. The compromise was made in the automatic assembly, where brass bushes were used instead of jewels. The brass bushes were prone to wear, and it is not uncommon to see cal.550 movements that have had both the upper and lower automatic bridges changed to the jewelled version.

The date version was introduced in 1967 as case ref.166.024 and used an Omega cal.565 movement with 24 jewels created in 1965.

The SM300 name suggests it to be waterproof to 300 metres but the Omega Vintage website and period catalogues list it as waterproof to 660 feet or 200 metres.

Ω Cases.

The bezel is 40mm in diameter on a 42mm case excluding the crown.
The case 13mm thick including the height of the domed crystal.
Lug to lug it is 47.5mm with a strap width of 20mm between the lugs.

 

PIC.2 – Cross section of the case.

Although the vintage cases have the same thickness as the current service replacement cases they appear thinner due to the shape of the lug ends.

After studying the logos inside SM300 cases it appears that Huguenin Frères Pic 6 produced the early cases and then Centrale Boîtes S.A., Pic 7 produced most of the rest. The earliest Huguenin Frères case I have seen was dated 1963. Some of the later cases were produced by other companies including Piquerez whose logo is illustrated in Pic 3 inside a 145.024 case back.

 

PIC.3 – Copyright: chronomaddox.com

With the exception of the crown which changed late ’67 early ’68 the case shape and dimensions did not change during production. However there are sometimes slight differences in the profiles especially between the different manufactures. A variation in the rehaut which surrounds the outer dial has also been noted. The majority of the rehauts are highly polished steel as seen in Pic 1 but some SM300s have a dark coloured rehault with a matt finish as seen is Pic 4.

 

PIC.4 – Copyright: virro (Omega Forums)

Inside the case back and enclosed in a triangle is the Omega logo Ω and the wording OMEGA WATCH Co – the last ‘o’ in WATCH Co is always smaller in size than the rest of the type. Copy below the triangle reads FAB. SUISSE and SWISS MADE.

ACIER STAYBRITE is the trade name for steel used by by Huguenin Frères. The Staybrite brand was created in 1954and belonged to Firth Stahl Verkaufs SA company a company owned by Firth Brown Group. It was subsequently purchased by British Steel who sold the business in 1979 to F.W. Hempel & Co the current owner of the mark.

Staybrite 1.4301 steel used by the watch industry at the time was composed of 18% chromium and 12% nickel, which is close to 316 L steel (16-18% chromium and 10,5-13% nickel) the industry standard at the time.

Below the case manufacturer’s HF logo follows the case reference and in the case backs illustrated above a dash and then the year of production. The year of production does not appear in all case backs.

The first three numbers of the case ref 165.024 comes from the following Omega table.

1 figure	2nd digit	3rd digit
1 – Gent’s watch	1 – Manual winding without seconds	1 – Non water-resistant
2 – Gent’s jewellery watch	2 – Manual winding small seconds	2 – Non water-resistant date
3 – Gent’s bracelet watch	3 – Manual winding centre seconds	3 – Non water-resistant chronometer
4 – Gent’s jewellery bracelet watch	4 – Manual winding chronograph	4 – Non water-resistant chronometer date
5 – Lady’s watch	5 – Automatic winding without seconds	5 – Water-resistant
6 – Lady’s jewellery watch	6 – Automatic winding centre seconds	6 – Water-resistant date
7 – Lady’s bracelet watch	7 – Automatic winding chronograph	7 – Water-resistant chronometer
8 – Lady’s jewellery bracelet watch	8 – Electronic chronograph	8 – Water-resistant chronometer date
	9 – Electronic

1 = Gent’s watch. 6 = Automatic winding centre seconds. 5 = Water-resistant. The 024 is the model number for the SM300.
The date version is numbered 166.024.

There are many theories regarding the reference S.C. One is that it is just an abbreviation of Steel Case. Another is that it stands for Seconde Centrale (centre seconds) but as can be seen in Pic 6 the S.C. was dropped at some point. Note also that the case ref.165024 does not at this stage have a full point in the middle.

 

PIC.5

 

PIC. 6

Pic 7 shows the inside a Centrale Boîtes S.A. case back. INOXYDABLE, which means stainless, has now replaced the word STAYBRITE. This indicates a change in the steel supplier for the cases. Pic 7 also shows that at some time during production a full point was introduced into the model number ie. 165.024. Many cases also had the date after the model number as can be seen in Pic 5.

PIC.7

The wording and logos on the outside of the case back Pic 8 remained the same throughout the production of the SM300.

 

PIC.8

Pic 9 illustrates that the very early cases (bottom pic) had a slightly different profile around the outer edge and case opening slots.

 

PIC.9

Ω Crowns.

The Naiad non screw crown (1962 to late ’67 or early ’68) is 3.15mm deep and 6.7mm in diameter with 24 grooves.
The screw down crown (late ’67 or early ’68 to end of production) is 5mm deep and 6.2mm in diameter with 22 grooves.

Pic 10 and Pic 11 show original Naiad crowns.

 

PIC.10

 

PIC.11

The Military issue SM300 was introduced in 1967 and part of the specification for the Military watch was a screw down crown.

The change of crown for non-military watches probably came about as a result of this so that the production of only one type of case was required. Pic 12 shows a screw down crown.

 

PIC.12

Ω Crystals.

Omega describe the crystal as ‘domed triple layer Hesalite’. My understanding is that Hesalite is Polymethyl Methacrylate (plexiglas). The domed crystal stands proud of the bezel by about 3mm and is engraved in the centre with the Omega Ω logo.

Ω Serial numbers.

 

PIC.13 

 

Each Omega movement has its own unique 8 digit serial number and the table below correlates numbers with date of production. Although the table is not 100% accurate it is a pretty good guide. Only the years of production of the 165(6).024 are listed.

 

The earliest SM300 serial number for a 165.024 I am aware of is 20’308’515.

1963 – 20’000’000 1964 – 21’000’000 1965 – 22’000’000 1966 – 23’000’000 1966 – 24’000’000
1967 – 25’000’000 1968 – 26’000’000 1968 – 27’000’000 1969 – 28’000’000 1969 – 29’000’000
1969 – 30’000’000 1969 – 31’000’000 1970 – 32’000’000

Ω Dials.

Fake dials abound for the SM300 and as this topic has been covered on many sites I am not addressing this issue within this guide.

Pic 14 illustrates the first dial style issued in 1963.

 

PIC.14

In the early 1960s the use of Radium on watch dials had been banned and Swiss dial makers took to marking their dials as T SWISS MADE T to show the dial contained no Radium. The ‘T’ stood for Tritium the new luminous material that replaced Radium. Some early SM300 dials were produced before marking a dial with a ‘T’ was made compulsory and are marked SWISS MADE only. Although these dials are rare they are original and the SWISS MADE only marking can be seen in some early catalogues. All dials had painted luminous hour markers.

Pic 15 shows the dial version introduced in 1967 that has become known as the ‘Big triangle’. This is usually fitted with sword hands.

 

PIC.15

Ω Hand sets.

Most SM300s had either luminous steel baton hands Pic 16 or the later larger luminous steel sword hands Pic 17 both with a luminous tipped white centre seconds hand similar to the Speedmaster. But there is third variation. Pic 18 shows a very early SM300 which has the broad arrow hand set used on the previous model CK14755. Pic 19 shows an illustration of this combination in a 1964 Italian Omega catalogue. A posting in 2009 by the owner of one of these watches explained that despite a lot of research he was unable to find out any more information. The ‘Extract from the Records’ that he received from Omega in 2006 stated that the watch was manufactured in March 1964 and sold in Italy which ties in with the catalogue date. Other than the example I used to own and the one featured in the 2009 posting I have not been able to find any more pictures of an SM300 with this configuration.

 

PIC.16

 

PIC.17

 

PIC.18

 

PIC.19 – 1964 Italian Omega catalogue.

Ω Bezel and inserts.

The bezel is 60 click and bidirectional. During the production of the SM300 bezel inserts there were a number of changes to the type style and size of the numbers.

As the current style bezel, in use at the time, would have been fitted as a service replacement many early examples have later bezels.

Certain bezel variations seem to be used more frequently on earlier models, especially the thin font variants A and B in Pic 20.

Current service replacement bezel, dials and hand sets will be Luminova rather than Tritrium and have a different glow as can be seen in Pic 21.

 

PIC.20

A – 1964 – Medium font – flat top ‘3’ – pointed top ‘4’ – no serif on ‘1’. No Tritium on 5 minute markers.
B – 1963 – Light condensed font – rounded top ‘3’ – pointed top ‘4’ angled serif on’1′. Tritium on 5 minute markers.
C – 1964 – Extra bold font – flatter top’3′ – flat top ‘4’ angled serif on ‘1’. Tritium on 5 minute markers.
D – 1969 – Medium font – rounded top ‘3’ – flat top ‘4’ angled serif on ‘1’. Tritium on 5 minute markers.
E – 1964 – Bold condensed font – rounded top ‘3’ – flat top ‘4’ – horizontal serif on ‘1’. Tritium on 5 minute markers.

 

PIC.21

 

 

Ω Military models.

In 1966 the British Ministry of Defence began negotiations with Omega to agree a specification for a diving watch to be used by the Military.

The final document was established on 1 January 1971, under reference Ministry Of Defence Document 66-4 Part 1 / Issue 2. To collectors these documents are known as the ‘standards MOD‘. MOD for Ministry Of Defence.

The illustration below is page 8 of the document and shows a very familiar looking watch. The full document can be viewed on the MWR forum using the link below. Scroll down to the 3rd post.

http://www.mwrforum.net/forums/showt…art-1)-Issue-2

The first Military SM300s were introduced in 1967 with the standard dial and sword hands. I understand that a few used the Naiad crown but cannot see how that fitted in with the MOD specification.

All the military SM300 watches had engraved numbers on the case back, the letter ‘T’ for Tritium in a circle on the dial and solid non removable strap bars instead of the usual spring bar.

 

PIC.22 – Copyright: Watchlovr (Omega Forums)

 

PIC.23

Ω Bracelets.

This section is actually the one with the most variables as bracelets are removable. When an SM300 was purchased new the buyer had a choice of either a steel bracelet or leather strap. At any one time at least two different bracelets would have been in production and available plus the possibility of a discontinued NOS bracelet also still being in stock at the Omega AD. Then consider that the first owner may have chosen a leather but later he or the next owner changed to a bracelet. Finally bracelets would have become worn and damaged and then changed to another or the clasp replaced.

For the sake of this guide I’m going with three bracelet types were available during the SM300 production run.

1506 – 1964-1966 – with end parts No. 16.
1035 – 1966-1972 – with end parts No. 516.
1039 – 1968-1971 – with end parts No. 516.

Just to confuse things further some clasps were marked with two numbers 1501 and 1035.

These original stainless steel bracelets have two sets of expandable spring links joined to non stretch links – one set each side of the clasp. The links are flat with the outer links as polished steel and the inner links brushed.

Pic 24 illustrates the 1506 clasp showing the Omega logo extending past the edge of the outer clasp. Pic 25 illustrate the outer clasps for both the 1035 and 1039 bracelets which were identical with the numbering on the inner clasp giving the bracelet its identity.

The inner clasps on these bracelets have a date code ie. 4 over 66 for the fourth quarter of 1966. This can be seen in Pic 26 which shows a 1966 1506 clasp.

 

PIC.24 – Copyright: Antoin (TZUK)

 

PIC.25 – Copyright: Omegary (TZUK)

 

PIC.26 – Copyright: Emeister (TZUK)

Ω Straps.

In addition to the bracelet the SM300 was also offered with a choice of leather or ‘Tropic’ rubber strap. Illustrated below is a period French advert showing the ‘Tropic’ strap.

 

PIC.27

 

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Well guys that’s the end of my ‘Quick Guide to an Omega SM300’ and I hope you have found it helpful.

Best wishes

JN