Maybe the bean counters in their infinite wisdom upon realizing the p01 and pcr, and compactD slides were all the same before roll marking consoladed them into one part. A couple less bins on the manufacturing floor saved them trillions of dollars... Who knows maybe once this old stock of slides is done we'll start seeing a common rollmark of "generic slide number 2 with FSS and LCI", etc. That can ride on top of frames with rails or not, steel, STAINLESS steel, or Al, fitted with threaded barrels or not...