I will just leave those 4 aside then.
Its got no SB markings on the Tecumseh motor.
Ive also got an older commercial Superswift here with a TVS90 Tecumseh motor on it. A bit newer than the SB520 by the look of it.
I think there was something else not victa with a tecumseh as well, Will have to look.
I dont mind em, they are not a bad engine, a bit of a pain to work on and those carbs hate water, definately not as idiot/abuse proof as a Briggs.