Picked up a cat 2cyl engine that was an oil test unit for mobile oil. Can anyone tell me anything on this engine. I can't find anything online. 02s18152 is the serial number. I've been a diesel mechanic for years never seen one before. 

looks like a 3500 series engine by the heads, rocker covers, lifting bracket, front/rear timing chest and front of crank as a guess. Looks like a Woodward fuel governor set up, in Cat 777B truck it would be on the opposite side on top above where the filters/canisters are on this engine, where governors is would normally have alternator and air con compressor for a truck.I hope this gives some idea of base engine design for you. 3508,3512,3516

I've been told it's 3502 modeled on the 3508 used to test oil. The man I got it from worked for mobile oil and he got when they were being scrapped by the company. He's since past due to cancer so I can't get anymore info from him. It's two cylinder and I had it running. I can't find another one anywhere. Im looking to sell it but no idea what it's worth or where to list it.

Im not sure on value to sell, in Australia we have Tafe and Cat institute for trade training they would look at im sure for future trades education, maybe you have a local body/company that could be interested for engine assembly training as a thought? At least it would be used minimal and be kept not scrapped.