I missed the "TESCO" stamp with was used by Collath's sons(Franz & Paul) after Wilhelm Collath expired(June 21st, 1906) and was for TESchner COllath. So they made it in their shop more than likely from sourced components post WWI, which would be a guess. It may be dated. Witten tubes were used on their higher offerings. The example is typical Teschner-Collath and was patented. The following is an advert showing the safety that I'm pretty sure came from littlegun:



Kind Regards,

Raimey
rse