New Old Stock AC heavy duty drop in oil filter P-115. GM # 5572288. Fits Cadillac 51-58. I believe it fits other mid '50's GM cars and trucks.  The box appears to be slightly discolored, maybe from water, but the filter and o-ring look good. There are a few small surface rust spots on the filter. It has been in storage for a very long time. I cross referenced the oil filter on the Wix filters site to a 51100. Full application chart can be found there. Auction is for one filter. I have 6 available. The boxes all show similar water type discoloration.