there shouldn't be a problem if nikon wants to use "D200", even if it is already registered by pileco. this is because pileco does not appear to be in the photographic equipment industry (i think) so there will only be very limited public confusion.
for example, if ferrari wants to name their latest sports car the "D70", there shouldn't be a problem as people are unlikely to confuse a car with the nikon D70 camera. however, if canon, sony, minolta etc would like to name their newest product the "D70" (especially if it's a camera), then there's a high probability that consumers may be confused and the trademark will not be allowed.
for example, if ferrari wants to name their latest sports car the "D70", there shouldn't be a problem as people are unlikely to confuse a car with the nikon D70 camera. however, if canon, sony, minolta etc would like to name their newest product the "D70" (especially if it's a camera), then there's a high probability that consumers may be confused and the trademark will not be allowed.