Mark on silver plate (?) tray

Here's a mystery. The tray body is plate, I'm fairly sure, someone has tried to test it. Handles, maybe not. They're marked - anyone decipher please?

 

On the left is as I see your first picture a 15(and a part of a "G") for 15 grms silver weight on the plated material.
As said many times by others, when it have square hallmarks is at 90% for french silver plate at the period when the weight for a piece was indicated, after it's a scale with the maker initials but not obligatory with the weight.