Mark,
Now that you mention it, my amp also has a stamped number on the tube panel: AF1564...64 being the common denoninator and the year I guess they were both built. My amp is black with a silver grill cloth and a rectangular plaque on the front frame, "Fender (logo), Fullerton , California". No other marks except the "NT" and "81" on the tube sticker and on the speaker magnet cover: "CUSTOM BUILT FOR FENDER EV 29, 137, 409, MADE IN USA".
Did that other site help you? I'll send you some pix if you give me an email address.
Be in touch if you get a valuation.
Gerry (Baltimore)
gerryhemming@comcast.net