I know what you mean about the history of machines. I bought a Viking 990 off ebay to have as a back up to my main machine. It was missing the footpedal, but had everything else with it. The machine had not been used - it still had the blue plastic film stuck over the needle plate, and no indication of any wear inside. This machine was made in the early 80's. DH gave it a good servicing, and it runs just fine.
I asked the seller, they said it was in a storage locker they bought, so had no idea of it's past history.