Here in the US that would be what we call a "Love Token". Back in the 19th century one would have one side of a coin shaved off then engraved with a persons initials, special date or rememberance of some sort. In this case a good luck charm. Minto could be just a nickname or a pet name for a loved one. The term "Love Token" came to be because often this was done by a young man and given to his special girl. I have read that often there were engravers working at Fairs and Carnivals. Some of the the work is very attractive. Look on eBay in coins & paper money/exonumia/tokens:love.