Wow, you must be right. Well spotted! I really didn't notice the bright spot and that the tubesocket must have been replaced. I guess this has been a mod done way back since the radio didn't show any sign of being worked on in the last 70 years as far as I'm concerned. The tube in question is actually a Telefunken AL1. According to radiomuseum.org the original tube is a E 453. The E 453 and AL1 seem to have similar properties, to my limited knowledge at least? The other three tubes are identical to the ones spesified on this page here:
https://www.radiomuseum.org/r/agabaltic_ah37_ah_3.html