I don't have a clue on your pewter 'find' , nicccky , as to value , but I'm forced to guess that this may have been sold at & or by/near(?) the museum you'd mentioned ... have you searched for that yet ? It just does not have the appearance of any 'famous' ones I've seen or recall !
Don't know much about replica coins , just a bit of knowledge about 'real' ones ... sorry .
Maybe worth ??
A posted image would so much help , if you can ...