I purchased one (the buyer offered at £40 each). Unfortunately I received the PMM-MD-53030-10 (opto-input) rather then the PMM-MD-53031-10 (COMS input) version.
The seller accepts the mistake and has accepted my return, but I am tempted to keep the module for the spare power hybrid.
BTW I cannot identify the optos on the pcb, so I suspect they are encapsulated in the smaller hybrid module adjacent to the input connector. The input connector for the step pulses is different also between the two versions of the module.