Hi guys, I'm trying to date both my Marshall 4 x 12 cabinet, and my JCM 800 head. The Cab is a 4 x 12, 1982 A.P., serial number 1859. And my head is a 50W Mk 2 Lead, serial number W21865. I've had both since the mid to late 80's, ans wouldn't part with them for anything!! Still going strong! Thanks very much!!!