[broadgage]

I suspect that 50 cycles will be fine. An induction motor will run slower perhaps giving a slightly less effective wash and spin action.
The motor in the program controller will also run slower thereby extending the cycle time and perhaps making up for the slower agitation and spinning.

The main wash motor may be a commutator type and not be affected by frequency.
Where was it used previously ? Private housing would be 50 cycles, but an American base might well have had its own 60 cycle generating plant.