That photo brings back fond memories of a great time and excellent tone, mine looked just like yours, and when I sold it, the heads were going for $500.00, it took me some time to actually sell it , but I wouldn’t let it go for less than $500.00, this was just before Christmas in 1983.I also own a 1979 JMP 2104 (2204 combo). The 2204 Heads seem to sell for a few hundred dollars more than the Combos.
In my experience and location prices per below:
Heads $1500 - $1900
Combos $1200 - $1600
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Still kick myself for selling it !!
Cheers