MMF Industries Plastic Key Receipt Holders - Houses the Key Receipt Slips. For use with the Dupli-Key System, the Key Receipt Slips record the key recipient`s name and date the key was issued. The Key Receipt Slip is then inserted into the Plastic Key Reciept Holder; the holder is hung with the master key for easy identification. Supplied 100 holders per bag. Current stock is either brass or plastic. Once brass stock is depleted, yellow plastic will be supplied. Yellow tone of holder may vary.