The first batches of all the AEA RCA replica mics (44's and 77's) were made using ribbons produced from NOS leftover RCA material. It exhausted pretty quickly but it showed how confident that AEA is in their mics and their ribbon formulation that they did that. I've heard nothing but good things about them, though I've never used them. I have a friend who has several of the real things whenever I need a ribbon. I've not needed the 44 for anything, but a pair of the 77's in a mid-side Blumlein pair are are bluegrass workhorses.