Apparantly the new u.s made big muff sounds exactly like the original… although this would probably be the second issue from the 70’s, thats what it looks like cosmetically.
Also the original transistors used in very early muffs are no longer available so replacements that are used dont sound exactly the same…
i’ve played with all of the muffs trying to get the best sounding one, its the first issue and i built myself one that sounds very close to it, much better than the russian one.
And for all us guitar players in the u.k that really pissed me off !!! a guy i know recently found an issue 1 big muff imaculate condition in box with manual and everything at a bric a brac fair… he payed Â£6 for it….