I think your phono stage must be a ZP 1 or 1.5 because there is only input option on it. The ZP 1 was apparently set up for MM cartridges and the ZP 1.5 was set up for MC. And the ZP 2 has two input options with a switch to select one or the either. Here is a white paper Steve wrote on the evolution of the ZP 1, ZP 1.5, and ZP 2.
https://www.decware.com/paper26.htm One way you could find out is to remove the plate/s (fastened by screws, not hex bolts) and snoop around for those Sowter step up transformers
By the way, quite a phono stage. No a fantastic phono stage if I do say so myself.
Good luck with sale