Wow, bet it sounds as good as the day it was built!
That's the amazing thing with these old amps, they were hand built with wired components which can be easily replaced. Modern amps are made with printed circuit boards and digital stuff which can be much harder to maintain. It's 57 years old and will still be going in another 57, assuming valves can still be found!
I didn't realise MK had one when I got it.
You still see it in some of Guy's studio diaries, Guy used it for bass on his album for example.