If you can not find a serial number plate, then you might want to steer clear of it. If it is missing, it could have been removed to conceal its identity. Basically meaning, it could be a stolen machine. Steering clear of that machine is a really good move unless you know 100% who you are buying it from. It might suck to pass up on that opportunity, but protect yourself be NOT buying it. When / if you find a secondary location of the serial number, call a BOBCAT dealer ASAP. They have the ability to tell you if it has been reported stolen. Believe me, if it was stolen, whoever owned it would report it stolen to BOBCAT or at least to the local police. Has this person said that they have owned it for a good long time?? What is its back story??