Ero
There is very little information about this company, and its date of foundation is not known, for which we can only indicate the upper limit of 1954, because in the same box in which it was found this leaflet there were also two heels of the monopoly of the free territory of Trieste ("Libero Territorio di Trieste"), established from 1947 to 1954.
The company was founded by Ernst Rodenhäuser, who had a small factory in Ober-Ramstadt and who in 1956, after the bankruptcy of Reform from Nieder-Ramstadt, bought its production facilities and buildings. There are also substantially identical pens produced under the brand Rodur, a brand which, like Ero, seems to derive from the name of the founder, and which is not clear whether it was earlier or contemporary. Since the instruction leaflets are identical, and since the packaging of a piston-shaped Hero bears the words Rodursal, there is no doubt that it is the same company.