That's not a 2000S cab. I think it's a 1968 Coliseum Sound system cabinet, and it originally came loaded with a pair of JBL D130's and a JBL "bullet" tweeter. That's why the top 15 is offset, and what that round hole in the top right of the baffle is for. The hole in the back was where the crossover/attenuator for the tweeter was mounted.
It's also too small, a 2000S measures 46" x 30" x 15" and I'll betcha your cab measures 40" x 24" x 15" (not counting the wheels).
Pretty rare cab, but not a 2000S.