Be careful. I had that exact model/age W202 where the ECU died 2 years ago, screwed up the whole car and all I could do with it was to sell it for parts (engine, catalytic converter screwed up apparently, as was the transmission, don't see how the ECU did all that). So if it was removed because it was faulty I'd avoid, but it might just have been taken to put into another car so who knows...
Anyway, ECU failure is a very well known fault in this car and will happen one day. There are lots of other things to look out for:
C-Class W202 1993 | Mercedes-Benz | Car Reviews | Honest John
Feel freem to disagree, I just had one of these and it all went horribly wrong. Paid £2000 for it, sold it for £350 with just 89000 miles