Different bracelets???

Are the bracelet different at 3717(04) (diameter 42) and the 3706 (diameter 39)?
Reason I am asking is that I can not fit an extra link in my bracelet.
I have a 3706 Spitfire and bought a used bracelet - the new type as on 3717. The bracelet fits but a brand new extra link (from a brand new 3717(04) doesn't????
A mystery???

3717's bracelet is 1 mm wider than the 3706

The ref. 3717 uses a 21 mm wide bracelet at the lugs, while the ref. 3706 uses a 20 mm wide bracelet. This was done, I believe, to maintain some sense of proportion between watch head and bracelet on a watch model which is 3 mm wider (42 mm vs. 39 mm).

3717's bracelet is 1 mm wider than the 3706

Not very smart - if that means all 3706 owners are stuck with their bracelets without the possibillity to get extra links. As it seems right now, extra links to 3706 are out of stock everywhere.

I - for one - have just bought a used 3706 bracelet to my Spitfire - and can not get the one/two extra links I need.

UTC bracelet should work

Because it has still the "old" case size and shape.

But there was a design change in the old pilot bracelets in 2004 or 2005. They both fit at the same lugs but the links are not interchangeable / compatible.

Tilo

UTC bracelet should work

Pardon my ignorance - but what is a "UTC bracelet"?
Besides that, you are right. Got the bracelet on to the watch OK - but the links from the "new" bracelet are slightly bigger.