Bob
Many thanks for confirming Pressed steel at adil. Puts my mind at rest and Les's too (balti was late 70's for me). Quite amazing how the weight has led me to the wrong conclusion. I'd have put money on cast iron. My BIR pan being black steel and feeling light in comparison but maybe that's another wrong perception. The black steel does rust just to muddy the picture.
I guess the 2 balti pans I have must be pressed steel (eBay and rusholme) - they don't rust and are heavy. Given the pic not authentic though. They do work though (caramelise, smoke, retain heat).
It does not help that my zaal omelette pan is very much what I would think of as pressed steel ie thin. It does not rust either but is no good to cook curry in (burns not caremelise)
Looking forward to chewytikka and Gav lscon's balti cook off. Be interesting to see how the authentic pan performs in comparison to the BIR Ali pan.