I use to deal in antique newspapers, Harper's Weekly and Lislie's Weekly. I saved a lot of Remington and Thomas Nast wood cut rag paper engravings, must have couple dozen, many are framed others are stored...
The embossed stamp may be the framer who framed it ? as in the maker mark of a company but without knoing when or where it was did it may be harder to find but i am sure someone can help