Hi Pat,
Thank you, good suggestion, and you're right on the money. It's a volkswagen part....Ate clutch master cylinder for a Vanagon ('82-'91), left hand drive, non-synchro. Part number W0133-1615742.
I ended up pulling out the whole pedal assemby as it was pretty grubby in there. Also, the pedal ratio for the clutch is too low for my set up (audi 016). It's about a 2:1 or maybe 2.5:1 ratio, making the clutch pedal both very heavy, and have too much throw. I think it should be more like 3:1. So, I'll modify the pedal box so it's an adjustable ratio rather than static, powder coat everything, install the new master cylinder and put the whole assembly back in the car. Really fun working down a deep footwell hole....