If you have the oil there are tribology labs that can test it for you. They do used oil analysis though it will be a little tough since you don't know the brand or viscosity used in the engine to start with. They would be able to give you a reading of metals etc. to give you an idea of engine conditions. It's pretty cheap to do the test and well worth it especially if there is any doubt about general engine condition. Just looking at oil tells you nothing about the oil, only a proper test tells the tale.