That is in fact correct. I'm pretty sure the spade cutout will be found on any number of "not-so-well-known" frames both before and since Mario. I myself have been cutting spades in lugs and BB shells since 1974. It's a common and natural thing to cut into a lugs.
La Mesa, CA
AFAIK, Peter Johnson�cut the ace of spades into his lugs�before Confente.