I am new to this forum and I am not even sure if it's the right place to post this. But each time I search something on optical issues this forum came up on search, so I thought I try the wisdom of folks here.

Does anybody know where I may obtain a copy of manual of Canon RK-2 autorefractor online? I tried to contact Canon and received no response.
I am planning to buy an used Canon RK-2 autorefractor in a private sale. The seller agrees to let me try the autorefractor for 1 week before deciding on purchase. It works "most" of the time, but every now and then it shows some "strange" reading. I obviously have questions about its accuracy, but figure there should a way to check/calibrate this unit, which may be described in the manual. The seller no longer has the manual.

Any help is appreciated.