Thanks for adding that link. I read that a few days ago but didn't link it as there was no mention of Erwin Pfohl when that was written in 2010.
There is family information from the Pfohls online and that confirms Erwin was at Josephinenhutte after Alexander Pfohl left. But there is very little information on him even though, if I understand correctly, he took over his family glass business and didn't die until 1975.
see here - you can cut and paste the information into google translate - it has quite a lot of info on Erwin Pfohl and states that in 1929 he was a designer for Josephinenhutte. There is no mention of him being there any longer than 1929 but that might be because the only source reference they have is a start date,then his further employment with Reich, so nothing definitive to state how long he stayed as designer at Josephinenhutte:
https://www.pfohl-glaeser.com/familientraditionMuch other information does come back to the book however the confirmation find of the photograph by Dr Arthur Traube is a key I think. I also wonder if the picture in the book is a watercolour rather than a photograph of a collection of pieces? I wasn't sure. Either way, Stefania must have found it somewhere so that is another piece of confirmatory evidence. Pictures are so much better than descriptive words when it comes to describing a piece of glass at least.