It's a Unicomp AFAIK.
That listing has been up for many months. The seller just keeps relisting it when the listing expires. Although initially when I saw it, it was for $10 cheaper. Don't quite understand the logic of increasing the price if it doesn't sell. That might work with some Mac users, but I doubt many IBMers will go for it.
In all fairness to the seller, a google search of the part number does seem to indicate that it is indeed quite rare. Although that doesn't really mean much, being IBM, et. al created so many different part numbers for the same keyboard but sold to different customers, which is likely what happened here. Albeit they added two unique keycaps. I've also seen standard part numbered keyboards with special keycaps, so no consistency there. If the keyboard was half the price, I might consider it for the novelty factor. For $100 and up, forget about it.