Two types of double loop trigger guards. As pictured above with serrations on front and good rail. The other is smooth on the front and no cross (1913/Pic) cuts on rail (?). I think the posted 57 is a GenII version.
That trigger guard is weird....I have one in FDE and love it. Someone will get a good deal with this un!!! Especially with the ammo! Before the ammo freak out years ago that's what I was paying fer that ammo!!!