I have seen and done the same thing. The desk manufacturer told me
that the rubber used on the feet degasses something like formaldehyde
until it is a few months, maybe a year old.
Checking with others in the office furniture biz, I found the same
Basically, they told me I was screwed as nothing they could do or
recommend that would take out the feet marks since it was now "in" the
finish. BTW, mine was a small printer.
If that is the case,(it is in the finish), you have nothing to lose by
trying a Mr Clean magic eraser, WD40, or Mayonaise.