The rock because in dirty for what I did to one like it. I took it from a gorgeous beach and lost it the next day, dooming it to suburban hell somewhere when it fell out of an unzipped pouch.

Or it escaped.

It’s so close to alphabetical, on average.
C = #3
USA = (21+19+1)/3 = 13.666
M = #13

Maybe use 3 letters
CAN = (3+1+14)/3 = 6
USA = (21+19+1)/3 = 13.666
MEX = (13+5+24)3 = 14

Anyway, they know. Content engagement and all that.