Inner Threaded Crown

[bobtheterrible]

Hi Guys,

I recently acquired an old Universal Geneve Unisonic case for a spare movement I had lying around. Sadly, it didn't come with a crown and to my bemusement the pendent tube was not what I expected.

It looks like this crown takes a screw-down crown with a thread internal to the pendent tube rather than on the outside. I had a quick look at Cousins, but none of their inner-threaded crowns matched the dimensions of my pendent tube (Im not even sure how I would check the thread pitch).

The outside diameter of the tube is 3.6mm which is larger than anything stocked by Cousins.

At this point I don't care if the crown I find is not original, I would just be happy with one that fits!

Does anyone know where I could source an appropriate crown or have any experience they could share? 

My fallback is to try and replace the pendent tube with a modern equivalent, but I want to avoid that if possible...

Dimensions: OD3.6mm, 2.8 hight, ID2.4mm approx

[AndyGSi]

What's the diameter of the crown need and have you thought about just using a standard, possibly waterproof crown instead of a threaded one?

[bobtheterrible]

Thanks @AndyGSi,

Yes, I have thought about using a standard crown but the issue is the outer diameter of the pendent tube. 3.6mm is kinda huge. Im struggling to find a standard crown with an internal diameter of at least 3.6mm.

Im guessing the outside diameter of the crown will be at least 6mm but judging by the case recess, less than 7mm.

[AndyGSi]

7 hours ago, bobtheterrible said:

Im guessing the outside diameter of the crown will be at least 6mm but judging by the case recess, less than 7mm.

I'm presuming you'd want the crown to sit in the recess so how big is it?

[bobtheterrible]

The recess is about 7mm in diameter (sorry, I didnt get a fully accurate measurement but confident of the upper bound of 7mm - will update when I get back from work). So yes, ideally to sit inside the recess. However, I don't mind if it sits slightly proud as the recess is not deep.

[AndyGSi]

I'll have a look when I get home tonight what my crowns around that size measure for fitting over the tube.

[bobtheterrible]

Thanks @AndyGSi that is very much appreciated!

I'm revising my previous estimate way down from 7mm to 6mm outside diameter of the crown. I remeasured the recess and my first estimate was waaay off....

[AndyGSi]

Looking at these I think your only option would be a 6mm General that's deep enough to suit your 2.8mm deep tube.

Top Left - 8mm Waterproof (3.5mm+ Tube)

Top Right - 6mm General (4mm+ Tube)

Both Bottom - 6mm Waterproof (2.5mm Tube)