There are tons of different muff circuits. The early ones weren't consistent with component values because they would just grab whatever was close.
Black russian muffs are a newer reissue of the big green one, but they aren't the same really. Big green ones have more midrange. Silver ones had a bunch of different circuits in them over the years, but the newest ones are decent. More scooped and smoother sounding, but easily modified. Word is that the new XO series bass big muff is very similar to the old big green ones.
There's a lot of info about muff circuits out there. Might want to read up a bit.. or say fuck it and just buy one.