Congratulation!
Could you please check between the lugs at 6 o'clock - is it the same reference? 7742 R?
As for the material, I suspect it is gold plated (that is often the case when the case back is steel).
I would check if you have any local watchmaker able to restor vintage watches or through your local GP AD ask to send it to Swithzerland.
Best
Blomman