I have a 10, not sure it works as well as it should as it's run from a phase converter but it slices through 10mm plate OK. I bought mine from ebay, the bloke couldn't get torch spares and shops wanted 300 quid to fit a newer torch
so he flogged it. I put a Trafimet torch on it. I did try and get torch parts, I sent pics of the torch to almost everyplace that came up on a google search for plasma torch parts. I found someone with parts, I think it was for a Telwin torch. But the parts were a lot more expensive than parts for the Trafimet torch.
If you mail murex they will let you have a copy of the manual.
I don't know what the 4 is like, the 10 I have is mid 80's, goes with the tig and mig;-) Just had a look at it and it looks newer than mine.