I've heard Safari is the one too Vic.
Although I remember hearing about a bug in them.
The bug had something to do with shaking the game at the right time and running the animal ladder all the way up ... think that what I recall anyway.
Might be discussed in that "Top Secret Underground Bingo Video" I sent you a few years ago ... Guess I'll put it on to keep me company next time I'm working on '56 Derby Day and see.