Failed anode dropper, discoloured to unreadable and o/c, presumably
100K as its fellow. Have to presume the DC blocking cap has failed to
cause that and replace that too, along with its fellow, and test the
valves just in case internal problem shows itself, but unlikely.
Dating JRC4560D has a code 3024D = 1993?, after year 2000 I thought 30**
on JRC meant 2003**
Standby sw has 9345
7W w/w has number 9153 on it.
General feel is 80s or 90s
So I'll settle on 1993 unless (wherever it is) that site for translating
Fender Tx numbers and Ser nos to dates , I can find again.