Help identifying 1920s (?) OMEGA

I have recently been given this watch pictured below. I believe it is 1920s/30s vintage. I have the original box and the (presumably) brass case has some signs of corrosion although the mechanism is fine and it keeps good time. Does anyone have any idea about the date and how much it may be worth?

dates to mid/late 1930s
http://www.chronomaddox.com/omega_serial_numbers.html
looks in excellent condition, given its age.

as you can see from the caseback, the case itself was made by Dennison in the UK, rather than in Switzerland. This was common around then to get around high tariffs on imported gold, or imported whole watches. Dennison produced these cases under licence from Omega.

Not sure of value.

What is the width of the watch? (excluding the crown)?

Thanks for that; very interesting. Its 30mm wide.

I am hoping that someone can give me advice on the best way to sell it? Obviously there's always ebay, but I'm not sure if this watch would appeal to a specialist collector.

It looks like a model 800. It has a [EDIT TYPO : 26.5 not 25.5😬 ], I guess a T1. The serial number is indeed around 1935.
Here is one in the 1933 catalog :


Mine says hello (the silver case has tarnished, I will have to clean it...) :

i think it is worth more to a collector than an 'everyday wearer' as most people will find 30mm too small (even with my small wrists, I've given up on 30mm watches). but someone here might be interested in it and PM you directly.

What a pity that Omega stopped using enamel dials. They are truly elegant and seem to last well, too.

There are several Omega Cushion watches on the bay with prices ranging from £350 to 500
http://www.ebay.co.uk/itm/Cushion-W...es_Watches_MensWatches_GL&hash=item2331325fde

What does SOB stand for

This is what I found on the net

http://watch-pop.com/vintage-watches/vintage-13421.html

The 26.5 was very successful and long lived, being produced from 1926 to 1950 and approximately 391,000 were produced. My accumulation of information regarding Omega movements shows the following variations.
CalibreID (year of production start)
Omega 26.5 SAV (1926)
Omega 26.5 T1 (1932)
Omega 26.5 T2 (1934)
Omega 26.5 T2 PC (1938 -- I don't have the exact date)
Omega 26.5 T3 (1940)
Omega 26.5 T3 PC (1940)
Omega 26.5 T3 PC AM (1942 -- I don't have the exact date)
Omega 100 (1949)
T indicates "transformation" and indicates a change in design.
PC indicates shock protection. This calibre was the first Omega wristwatch with shock protection.
AM indicates antimagnetic.
When you next have the case back off the watch, the calibre indication (and perhaps some additional information) is engraved under the balance wheel. It it awkward to see without removing the balance wheel, but it will tell you exactly which variation you have and more accurately date your watch.
For instance, I have a cushion shaped watch with the engraving 26.5 SOB T1. It appears in this way:
26.5 SOB
T1
S indicates savonette (French for hunter), meaning the relationship of the crown to the subseconds dial is 90 degrees apart, rather than opposite, as in hunter cased (covered) pocket watches, as is traditional for wristwatches, crown at 3, subseconds at 6. Open faced pocket watches have the crown at 12 and subseconds at 6, an arrangement referred to by Omega as Lepine (L). As it was the standard arrangement for pocket watches, it was generally omitted as it was the default.
O indicates it is the Original thickness of the movement where variations were available; other indications were P for Plat(French for thin).
B indicates the movement is of base quality, where higher quality variations were available.
These designations were helpful when pocket watches were most popular. Customers could order several variation of quality for the movement and designate several different case materials. In 1926, pocket watches were still more popular than wristwatches.
I believe later version of the movement dispensed with the SOB type designations, but am uncertain of when (and if) this occurred.

Thanks for the explanation H most enlightening and interesting