Big Muff Pi Black Russian Pots
Disconnect at least two of the wires.
Measure the end to end resistance on the outer tags. That tells you the pot resistance value.
Turn it to centre position and measure the resistance from the wiper to one end.


If the centre-end resistance is half of the track resistance then it's a linear pot.
Otherwise it's a logarithmic (audio-taper) pot.



All this assumes that the track and wiper are intact. If not you'll have to wait for the Russians to arrive.