I have a vintage 1964 Vibroverb that I bought at a pawn shop a couple years ago. I got a good deal, but still had to shell out some bucks. It appears that someone replace the orig. speaker with a 1968 Jensen. I want to replace it with a period correct JBL D130F. The date code on the amp is January 1964. Was wondering if anyone out there could tell me what serial number would correspond to late 63 or early 64 JBL D130F, and the general cosmetics to look for?