I was able to buy a bundle of old "Bergsteiger" magazines and found an interesting article about ice pitons in a 1939 issue. The article is written in old German script and is difficult to read.
Here is a short summary:
Ice pitons were invented by Fritz Rigele in 1924 and tested for the first time with Willi Welzenbach on the north-west face of the Großes Wiesbachhorn.
The Rigele/Welzenbach ice piton is an iron pin up to 32cm long with a ring, barbed at the tip.
The first disadvantage is, on the one hand, that the ring eye is often crushed when hammered in and the the ring is no longer movable.
Secondly, the piton often loosens out of the ice when exposed to heat or stress, and because the teeth are only on the conical tip, the piton no longer has a hold.
In 1938, the engineer H. Jungel from Liezen (Styria / Austria ) invented a new ice piton.
The new ice piton is slimmer, shorter and the barbs are distributed over the whole length of the pin. The ring is in a lateral eye so that the hammer beat no longer squeezes the eye.
Two ice pitons in the Ashby Robertson collection