There were two barter stores run by the Allied Military Government in Germany after WWII -- one in Frankfurt and the other Berlin.
The stores were created to help curb the blackmarket. Germans could bring their personal items (Zeiss cameras, shoes, whatever) where they were appraised on a point system. US military personnel could also bring items in for the same purpose. They were then given this amount in coupons which could be used to buy anything in the store. The store took a cut for operations. The unit denominated certificates were not redeemable for cash.
The Berlin store was not open long. The Frankfurt store was open long enough for there to be a number of different series of the coupons. When the Frankfurt store was closed in 1948, the remaining inventory was sold off and the money it had left over was donated to a German youth organization.
The notes are relatively scarce with the higher denominations (they were issued up to 100 units) being rare.
The number SB611 referenced in the
ebay listing is for the Schwan-Boling catalog World War Two Remembered which is the bible for WWII numismatics. All of the barter store unit coupons are listed in that catalog.