Hey, that's not what the coin itself says. the reverse legend claims: MONETA ARGENT. Although, there's a proverb: If you see a plaque on a bull's cage which says "Lion" don't believe your own eyes.
You went a little too far on your Friedrichs.
Friedrich Wilhelm III replaced Friedrich Wilhelm II in 1797. In his turn Friedrich Wilhelm II replaced Friedrich II in 1786, but FW II's coin types were different.
So what you have is the last year of Friedrich II who ruled 1740 - 1786.