The putter head is cast stainless steel. I would estimate that mine is, at least, 30 years old. Being that old it was never meant to have an oil bath after each use or to hide in a cover between holes. There are no major dings in it, although I admit using it to express my occasional displeasure by tossing it to my bag.
This is the classic design that has won at every level everywhere. I read that there are over 50 imitations of this design in manufacture. The most notable clone is the Scotty Cameron Newport design. Cameron may be made from better materials and it is CNC milled, but the shape is still Karsten Solheim's vision.
There is really little to fault. I have noticed that it is somewhat prone to get caught up in the grass early or be "stubbed". Maybe a more rolled leading edge would be better.
For me, this is the optimum design and the original. Perhaps, it is even a collector's item. The Cameron's sincerest form of flattery may be a better instrument, but they cost $250-$325 at full retail. 2-3 new Ping Anser 2s can be had for that.