Sorry I cant offer any advice but I will say that it is pretty cool whatever it is struck on 
PaddyB's suggestion makes sense that it is part of the Plate stamp, apart from that I am clueless
I have a 1775 that weighs in at 7.41g and in hand shows some flan oddities, not sure myself what they are but we have to remember that these are not " official " issue coins so anything was fair game.
My 1775


PaddyB's suggestion makes sense that it is part of the Plate stamp, apart from that I am clueless
I have a 1775 that weighs in at 7.41g and in hand shows some flan oddities, not sure myself what they are but we have to remember that these are not " official " issue coins so anything was fair game.
My 1775























