I know if I had just purchased a used tractor and decided to drain some oil out to check, going solely on appearance, I would have thought it's been a while since the previous owner changed the oil!
RK 55HC,ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC
or it would have sucked and burned it's own juices...
I have a ford 3000, from 68.. when i got it looked like original oil... I cheged the oil, and it was coal black the first moment it circulated thru the block. took another oil change a few hours later after getting her warm, to clean her out so she didn't soot up in 5 minutes..