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.