1930s 'clamshell' cases

Mafkees · Sep 10, 2019

Hello,

I recently purchased a 1930s Eterna that features a 'clamshell' case (serial 242xxxx so it looks to have been produced in 1931). It will need a movement service before it is ready to wear and I suspect the crown to be a service replacement from the past. I did some reading-up on the history of these cases (most notably: https://www.vintagewatchstraps.com/waterproof.php) but I was unable to find any information regarding the crown's part in providing water resistance in these '30s cases.

My example:

Crown close-up.

I did find some similar examples that all feature a sturdy crown, which leads me to believe my example has a replacement crown.
https://omegaforums.net/threads/cyma-watersport.92960/#post-1205178
https://omegaforums.net/threads/early-eterna-waterproof-need-input.90685/#post-1173976
https://www.ebay.com/itm/Rare-Stain...344672?hash=item4d9b8016a0:g:dpAAAOSwEAtdG7Kp

Hopefully our combined efforts can lead to 1) establishing the authenticity of the present crown; and 2) a part number of the correct crown or pointing me into the right direction to acquire one.

Kind regards,

Matt

Oku · Sep 10, 2019

I cannot contribute to the crown question, but beautiful watch! Congrats!
And Dibs!

Vitezi · Sep 10, 2019

The shape of your crown leads me to think your crown may be original, or at least it's the right style. Early "waterproof" designs like yours likely relied on stem seals, gaskets, and some sort of case clamping force to provide a little bit of water resistance. Other designs featured rubber gaskets inside the crown with a "screw-down" action, or double-case designs where the crown was protected inside a second case cover.

Have you opened yours up yet, to see how it is put together?

Mafkees · Sep 10, 2019

Vitezi
The shape of your crown leads me to think your crown may be original, or at least it's the right style. Early "waterproof" designs like yours likely relied on stem seals, gaskets, and some sort of case clamping force to provide a little bit of water resistance. Other designs featured rubber gaskets inside the crown with a "screw-down" action, or double-case designs where the crown was protected inside a second case cover.

Have you opened yours up yet, to see how it is put together?

Thanks for your input. The watch is not yet in my physical possession and the two pics above were posted with permission from the seller, as is the one below. I don't have the means to properly open the case so I won't try in the first place. The watch is to be shipped to a watchmaker soon.

What sparked my theory about a replacement crown is the discoloration, which strongly resembles chrome plating wear. The case is Staybrite so I would typically expect a crown of the same material. Now that I consider it: it is a very early example so it's possible that stainless (Staybrite) crowns weren't available yet at that stage, due to manufacturing process limitations. Thoughts?

Here's a case back shot for reference.

Canuck · Sep 10, 2019

If you are concerned about what part the crown plays in the water resistance because you will be wearing the watch in water, I have one word for you! Don’t!

Mafkees · Sep 10, 2019

Canuck
If you are concerned about what part the crown plays in the water resistance because you will be wearing the watch in water, I have one word for you! Don’t!

Lol! Don't worry, not a chance!

I'm just a sucker for original watches and I think this example warrants the efforts and expenses of restoring it with an original part, if it turns out I need to.

Oku · Sep 10, 2019

Mafkees
What sparked my theory about a replacement crown is the discoloration, which strongly resembles chrome plating wear. The case is Staybrite so I would typically expect a crown of the same material. Now that I consider it: it is a very early example so it's possible that stainless (Staybrite) crowns weren't available yet at that stage, due to manufacturing process limitations. Thoughts?

That is not uncommon. Gold watches also usually don't have solid gold crowns except for some brands like Patek.

pitpro · Sep 10, 2019

Bracelet may be original.
Looks to be a Bonklip.
From the web:
The Bonklip was developed in the 1920s and 1930s and was issued on British military wristwatches in the 1950s and 1960s, post-WWII. These bracelets were mass-produced, easily adjustable, and machined from stainless steel (in fact, they were some of the first mass-produced stainless steel bracelets). Though bracelets were generally not offered as a standard option on the earliest Rolex watches, there is evidence that some may have been sold with Bonklips in the 1930s and 1940s.

bubba48 · Sep 10, 2019

Not from the 30s

Mafkees · Sep 10, 2019

pitpro
Bracelet may be original.

Thanks! The watch was a barn find originally and the bracelet was attached. The seller mentioned the bracelet is original to the watch.

Radiumpassion · Sep 11, 2019

Based on other examples I think the crown is a replacement. These watches
also feature a split stem patent that in some cases should be left alone.

Vitezi · Sep 11, 2019

A few more clamshells in these threads, mostly from a later period though:
https://omegaforums.net/threads/lets-see-some-sq-clamshell-watches.71341/
https://omegaforums.net/threads/early-eterna-waterproof-need-input.90685/

Some old Eterna tanks in this thread, with a thicker-looking crown:
https://omegaforums.net/threads/eterna-clamshell-calatrava-hahahahah.56550/

Mafkees · Sep 11, 2019

Thanks for your insights.

@Radiumpassion any clue of the part number or where I should go to find one, presuming this applies to my example?

Radiumpassion · Sep 11, 2019

Sorry, they are nearly impossible to find. And if you break the
split stem you are in trouble. Post some pictures when it arrives, I
have some crowns here but I need measurements of your tube. And the
lenght of the stem.

Mafkees · Sep 12, 2019

Radiumpassion
Sorry, they are nearly impossible to find. And if you break the
split stem you are in trouble. Post some pictures when it arrives, I
have some crowns here but I need measurements of your tube. And the
lenght of the stem.

Absolutely, I'll be in touch. Thanks!

kingsrider · Sep 12, 2019

I have this little Eterna. It sits next to my Rolex Bubbleback in my collection as an example of early waterproof watches.

Mafkees · Sep 12, 2019

Interesting. This one also has the 'sturdy' crown but it is a later example.

bubba48 · Sep 12, 2019

Not a clamshell, but this is probably the first Eterna "diver"

Radiumpassion · Sep 13, 2019

Very cool @bubba48

I have a «Roa watch co» in the same tre tacche case, cromed brass case right?

To get back on track with clamshells. I got this at the fleamarket the other day.
Got it mainly because of the GF bracelet, but I did not see it was a Eterna before
I got home😬

bubba48 · Sep 13, 2019

Radiumpassion
Very cool @bubba48

I have a «Roa watch co» in the same tre tacche case, cromed brass case right?

All stainless steel 😉

1930s 'clamshell' cases

Mafkees

Oku

Vitezi

Mafkees

Canuck

Mafkees

Oku

pitpro

bubba48

Mafkees

Radiumpassion

Vitezi

Mafkees

Radiumpassion

Mafkees

kingsrider

Mafkees

bubba48

Radiumpassion

bubba48

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