Host coin: Japanese Yen, 1891.
It appears to be the Coat of Arms of the city of San Juan, Puerto Rico.
Certainly seems to be. Thank you very much!
For the curious, a post was made of another chopmarked piece, a 1904-S Philippine Peso, bearing this mark as well (https://www.coincommunity.com/forum/topic.asp?TOPIC_ID=116044). It seems likely to be a modern fabrication.