Near as I can tell, my book "The Standard Directory of Proof Marks" shows them to be Spanish. ( in use 14 Dec 1929 - 9 Jul 1931)
The first mark on the frame designates the Eibar proof House. The next "R" is for final proof of a revolver and should be on all major parts. The "E" stands for guns imported from a foreign country. The last "F" is probably the mark for the inspector that did the proofing.
So it looks like the gun passed through Spain for commercial sale around 1930 or so.

Buff, I agree! I noticed that the side plate screw looked a little "buggered" and then overplated in addition to what you mentioned...

__________________
Dean
SWCA #680 SWHF #446