Right! I had forgotten about that. It's Greg Gagliano and Greg Huntington. @Wally has pointed me and others to these before as invaluable articles on dating Fender amps. I had forgotten about them in this context, though. Go to www.ggjaguar.com/biblio.htm. There you'll find a six-part essay by Gagliano from 1997 (x2), 1999, 2001, 2002, and 2010 on "Dating Fender Amps by Serial Number." They were all originally published in Vintage Guitar Magazine, and I think some of them include guesstimates at production numbers. I've read them all, but I don't recall all the details now.