Hi Artdeco, welcome to the forum.
Thank you very much for the correct answer. It was right under my nose as mentioned in the book
World Hallmarks volume Europe 19th to 21st Centuries. The Paris Mint Assay Marks. The Monnaie de Paris manufactures historical, commemorative award medals, and other objects. Frm 1907 to 1993, domestic medals, or those destined for export, could be stamped with one of the following precious metal hallmarks; winged O for gold, winged A for silver and in 1910 winged PL for platinum. All came with a number to indicate fineness for silver 1=950 and 2=800.
However there exist an extensive list of Paris Mint numismatic hallmarks, one example, like in our case, of one of the more common marks used in multiple variations is the cornucopia or horn of plenty mark, and the number 1 indeed could indicate sterling=925:
Best,
Oel.
