OK, I've come across a pot that has me puzzled:
a. There is no mark. Handles are brass and the measurements are precisely metric (24 cm diameter). There are no marks, not even a number.
a. The sides are about 2 mm thick but after close inspection, and they seem to be clad with a thin copper layer. It seems to be a distinct layer. There may also be another layer on the inside (tri-ply). OK, so I think it's an undesirable superficially clad pot.
c. The bottom of the pot has worn thin and it appears to have copper showing through. The bottom appears to be thicker (measuring outside dimension versus inside dimension -- roughly 2.5 to 3 mm). There is a thin line that you can feel all around the lower sidewall, roughly 1 cm from the bottom.
What is this?