Agree with Pogre. It's pretty clear from the sticker that it's a salesman's sample. Sold to one below retail or maybe even below wholesale, so not for resale in a store. All I can add is that those are the oldest 901's I have ever seen.
I hope you have the active equalizer for them. They sound quite bad without it. If not, maybe find one on-line to complete the set for practical and historical purposes.