French gold hallmarks

[malibu flea market]

hello....this is my first time posting....i have a lovely diamond(OMC and rosecut) necklace that is white metal on the front, and ‘rose gold’ on the back. there are 2 hallmarks: what appears to be 2 eagle heads??
i know one eagle head means french 18K(please correct me if i’m wrong)
why would there be 2?...or maybe the second eagles head is not an eagles head??