Omega Seamaster Denisteel 1956 Cal 420

[Curiousniall]

Hello everyone, long time lurker and first time poster, I have a small vintage Omega collection and have a think for steel time only pieces.

I recently acquired this Seamaster, it has a Denisteel case and cal 420 movement. The case back is stamped 3420, but does anyone know if this particular model had an actual reference?
The serial number puts it as 1956 movement wise.

I have seen a few Denisteel cased watches labelled as a reference 720 but with totally different case designs. Some similar to this and others not.

Does anyone know if it had a reference? was hoping to check as I wanted to make sure the crown was original to this and if not acquire an appropriate one.

Thanks in advance

 

[X350 XJR]

Cases made by Dennison do not have corresponding Omega reference numbers.

 

[padders]

Well some do in fact, and this is one. Not many its true, but I can think of a couple. The Swiss model that corresponds with the OP watch is double stamped with 2759/2761, I was always pretty sure this is a UK made version of the latter and the 2759 was the sub second version. Like this, the Swiss version is a 420 movement manual wind centre second fat lug from the mid-late 50s with a plain snap on back. The number in the back seen above isn't a model number, its a case serial, hence the last 2 digits are stamped on the rim of the mid case to ease marrying them up on the work bench. I have no idea what model number Dennison themselves allocated to this, if any.

That crown was fitted to mine and I've seen it on other UK made Seamasters so I think it is original. The Swiss versions used the clover crown but that isnt what you have.

Here is mine, now moved on. Mine had a serial just 600 higher than the one above. I dated it a bit later at 1958.

Edited: Dec 13, 2023

 

[Curiousniall]

Thanks for the information, great to know the crown is original and about the corresponding Swiss models.

Its interesting that they did this to avoid paying taxes on importing cased watches!

Regarding the date, Ive said 1956 based on the serial number lists that can be found online, is there any way of being 100% sure on date? I know sometimes movements ended up lying around awaiting casing.

 

[padders]

With the solid gold stuff certainly yes the reason for local production was to avoid duty, with the steel stuff though I don't think the same imperative applied. The British were instrumental in developing stainless steel and other alloys for watch cases and the Swiss adopted proprietary British patents like Denisteel and similar so it may have something to do with that, or may just be that as they already had the gold working relationship it made sense for Dennison to branch out. You don't see steel locally cased stuff much beyond 1960 so it didn't last forever and either the British patents lapsed or more likely the Swiss just developed their own alloys that didn't require payment of licence fees.

I am confident on my date estimate for a couple of reasons, I think I have a more accurate list than the one you've looked at (and have data of my own on several 50s watches) and secondly I've had solid gold Omegas with 16m serials with 1958 date hallmarks, and our watches have serials at 15.98m so near as dammit the same. You can't be certain though since it could be that batches of movements were manufactured out of sequence or made together then cased at different time. If our 420s sat on the shelf in Handsworth for years, our watches could in fact be later, they were making Swiss straight lug Seamaster well into the 1960s for example.

Edited: Dec 14, 2023

 

[Curiousniall]

padders

With the solid gold stuff certainly yes the reason for local production was to avoid duty, with the steel stuff though I don't think the same imperative applied. The British were instrumental in developing stainless steel and other alloys for watch cases and the Swiss adopted proprietary British patents like Denisteel and similar so it may have something to do with that, or may just be that as they already had the gold working relationship it made sense for Dennison to branch out. You don't see steel locally cased stuff much beyond 1960 so it didn't last forever and either the British patents lapsed or more likely the Swiss just developed their own alloys that didn't require payment of licence fees.

I am confident on my date estimate for a couple of reasons, I think have a more accurate list than the one you've looked at (and have data of my own on several 50s watches) and secondly I've had solid gold Omegas with 16m serials with 1958 date hallmarks, and our watches have serials at 15.98m so near as dammit the same. You can't be certain though since it could be that batches of movements were manufactured out of sequence or made together then cased at different time. If our 420s sat on the shelf in Handsworth for years, our watches could in fact be later, they were making Swiss straight lug Seamaster well into the 1960s for example.

Thanks for this, I guess I will never know for sure on date, I thought it would be kind of nice to acquire one from each year eventually!

I got my information on the duty from a site that actually sold this very watch:

https://www.susannahlovis.com/antiq...intage-omega-seamaster-denisteel-wrist-watch/

They say that duty was paid on assembled watches?

Might make sense as now there are different levels of duty paid on goods via the different tariff codes with movements having a separate code and % vs a complete wrist watch?

 

[padders]

Note that site has the date for a 16.07m example at 1958. I hope you didn't pay £2,750 for yours! These trade in the mid hundreds usually. The Burlington Arcade gang pick a number and then multiply it by 5 to get a selling price. Nice stock but they are chancers

Edited: Dec 14, 2023

 

[Curiousniall]

padders

Note that site has the date for a 16.07m example at 1958. I hope you didn't pay £2,750 for yours! These trade in the mid hundreds usually. The Burlington Arcade gang pick a number and then multiply it by 5 to get a selling price. Nice stock but they are chancers

No, it was £280