It seems there is no trademark registration for "Humming", just these odd ones...
"J.F. Humming", Sept. 11th, 1972:
"Humming Custon" (yes, that looks like an 'n'), same day:
Maybe I wouldn't have registered "Humming" either if I had already 2 trademarks with that name in it. OTOH, they made sure they register every other thing in the world combined with the ending '-star'.