It's a mystery! What kind of bass do I have?
Honestly? Darned if I know. And, sorry, please don't send me photos. They are unlikely to help unless the builder's name is printed on it somewhere. It may need to be examined by a luthier who has a long history of seeing many instruments.
Seriously, there are a lot of makers out there, and most basses have a pretty generic look to them that prevents immediate identification. I'll assume if you found a brand name on it you've googled it, and if you get zilch back, its true maker may continue to be a mystery. And if the label says Antonius Stradivarius Cremonensis Faciebat Anno 1709 or some such nonsense, as you'll see in many violins, don't get excited. It isn't one.
It's quite common for factory basses to come unlabeled or with custom labels for a particular music store. That's been done for many years and continues to be a popular practice in all sorts of industries, so stores or sellers have "their own basses" that cannot easily be compared. Also, you'll find appliances, mattresses, etc., with different model names so you can't really tell if Store A has the same mattress as Store B at a better price. Therefore, the name on your mid-20th century bass could be a long defunct regional music store in the midwest. And ain't it funny how all those Chinese basses have German names??
I know there's a certain cool factor about owning an old Kay or Juzek*, but when you get beyond a certain period of time, if the bass sounds good, it is good. Who cares who the guitar player's parents were if he really rocks!?!
*my own "Juzek" bass has no label but has some identifying characteristics -- that could have been imitated by someone, I guess. But I was told it was a Juzek by a couple luthiers, one says pre-WWII, one says post-WWII, and I choose to believe that, regardless of reality. But it really doesn't matter unless I want to sell it to someone to whom it does matter.