Those German radios from the 50's were part of Germany's recovery from WW II or "The Economic Miracle". Literally millions of these type of radios were sold. I have about 5 of them. They do sound good too.
The only thing I can think to tell you about these is that when they were built the companies used cheap components. Paper capacitors, etc. Just about any of these radios can always use a cap redo. Done properly with modern caps, these radios can last another 75 years or so easily. It looks like the ones you acquired are in mint or very near mint condition.
And for radio listening a nice wire antenna doesn't hurt. I put on up in the attic and in the evenings I can get lots of European SW stations.
My favorite part of the radios is the wood finish. They really did those nicely, the high gloss just looks wonderful. But if the surface gets scratched, there is no easy way to fix the scratch. From what I have read the chemicals that were used to create that deep gloss finish were highly toxic and are no longer being made.
It's one of those things that made these old radios so beautiful!
And we know it is not. 
