Two, maybe more, but they were prototypes and I am clueless towards any effect/role they played.

I've even seen design works for Maus IIs, these things never got pasted the drawing board, but they were titans, one man believed he could slam around ten 88mm Self-propelled on the thing.

Their were best off producing more Panthers and Tigers, the Maus sucked up alot of resources and to no avail it seems.