If you have the books on the NW Trade guns, they have many pics of original guns with tacks.
Trade Muskets or Northwest Guns by Bill Newton
Success in the North American Fur Trade/Conner
The Northwest Gun/Hanson
Trade Guns of the Hudson's Bay Company 1670-1970/Gooding
These 4 have the most pictures. Also, the original tacks were the square shanked kind. The Trunk Shoppe in Harrisville, WV carries the original square shanked brass tacks. I think that the ones that Track has have round steel shanks, maybe? As long as they have a solid brass head, I guess it wouldnt matter, but if they are just iron tacks that are brass coated, then they will wear off and show shiny steel underneath. Remember, less is more.
B