Source: berkelmuziek.nl 

This rare bird is really an enigma. Unfortunatley no serial # is provided, so we have no idea when it was made--or for that matter where. Was it a Graslitz horn? Marknaukirchen sax?

My money is on Marknaukirchen. Why? Well, let's take a look at a few of features:

1. Yes, it has split bell keys, but that's about all that gives us an indication of its age. 

2. It is keyed to high F. Modern JK basses are only keyed to high Eb. 

3. Note the left pinkie cluster, that is something we see in the earlier Tonekings. Not sure when exactly the switched to the more modern left pinkie cluster, but they had it in the 80s already--and quite possibly even earlier.

NB: The thing to remember about JK bass saxophones is that they were all made by hand, and are a reverse-engineered version of Conn's 14M. So... Based on this, we really can't draw conclusions on only 1 sample. Given that there have been less than 200 bass saxes built by JK in total (according to the company itself), without a serial #, any guesses about its age are just that: guesses. 

Whenever it was made, it is in amazing condition, and shows no evidence of major past repairs. It was also rocking a fresh overhaul at the time of sale.