This is a custom construct, based off of a '74 Marshall metal-panel Superlead, except that it's 50 watts rather of 100. Totally hand-wired with high-quality elements, it's an error! Built by regional amp home builder who sells these on eBay for 500 - 600 dollars for a similar chassis. Less than 10 hours of use this one (too numerous amps!).
Framework only. It will fit both a small-box or big-box Marshall head taxi (conveniently available through Mojotone, amongst many others).
Tube set is 3 12AX7s, and 2 EL34s. Very strong build, very strong reliability, extremely solid tone.
500 dollars. If it doesn't offer, it's off to eBay.