Numismatically, this coin is known as a "love token." As described by River City Coins -
"Most love tokens were made in the late 18th and 19th centuries. The practice began in England in the 17th century and migrated to America in the early 1800's becoming popular in the United States around the time of the civil war. The US Government outlawed the practice in the late 1800's. Individuals would take their coins to a jeweller or engraver who would smooth out one (and sometimes both) sides of the coin and reingrave it with the initials or name of the intended recipient. They were usually given as an expression of love and sometimes as a proposal of marriage. Mostly unique, they were a precious and cherished gift. Seated dimes were the host coin for the majority of American love tokens, but they are found on all denominations from half-cents to $20 gold pieces as well on coins from all over the world."
http://www.rivercitycoins.com/exonum...lovetoken.html
http://www.jhonecash.com/coins/coin_...r=lowest_first
This was obviously make for someone with close ties to the team, possibly a player from the Alert Base Ball Club. Due to the appearance of soldering remnants on the obverse, this was once either attached to a pin back (to be worn on clothing) or attached to a pocket watch chain (as a fob).
http://www.icollector.com/Newfoundla...arce_i13822739