unredeemed article; foreclosed item
Refers to an item that was used as collateral and was not redeemed, so it becomes the property of the lender. Often used in the context of pawnshops or secured loans.
I bought an unredeemed item cheaply at the pawnshop.
質流れ is a more common term for unredeemed pawned items, while 抵当流れの品 is a more formal or legal-sounding expression often associated with mortgages or secured loans.
Compound of 抵当 (mortgage, collateral), 流れ (flowing, here meaning forfeited), and 品 (item). The term literally means 'item that has flowed from collateral'.