Identifying Gold Hallmarks

by josphine
(italy)

I have inherited two brooches, and trying to identify the gold hallmarks on the back. The first one, is two gold leafs with the marks OMA 750 and what looks to be 52 AR (in this order) it does look like the oma could have the letter r or c in front of it, but its smudged.

The other brooch is a decorative leaf, flower and pink stones, with what appears to be 98? the 8 could be a 5, the last letter/number is smudge, the 750, then the letters MA,
I know what the 750 means, but I have searched high and low for the other marks, but with no luck.
MANY THANKS