Pls help identify initials mark on silver watch case

[labrat]

I have a silver watch case with an oval mark containing initials STR inside. There is another mark (it's the blur on the left side of the pic) which looks like it is the swan hallmark for French imported goods or small guarantee.

The case is a pocket watch case converted to a wrist watch. Contained an old movement (circa 1936). The dial was fabricated/fake and is of no help identifying the origins of the watch. That is why I only shot the back.

I've combed through this forum as well as the website and have not come across anything resembling this mark.

Any help is much appreciated.

Here are the pictures:

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[labrat]

Update:

I used a microscope to look at the Swan mark and it looks like there is a letter 'D ' in the top right above swan's tail.

Also, the watch case has two covers on he back (the movement cover and the decorated cover). Both covers have the the swan and the initials marks.

[biscuit]

I can't help you identify it, but rather than "STR", I might try turning that mark upside down, and reading it as "JS" with a sword separating the two letters.