Let me not hi jack the OP, but having just picked up a set of 6 division plates at a good price, I am going over my own dividing head, while making the required modifications.
This unit is made by "The K. Mfg. Company." from Wisconsin. It is quite a relic and may have historical value if not hysterical significance ;-).
It is fitted with an interesting three jaw chuck made by Union Mfg. that allows some adjustment due to the play in the ring gear that dirves the independent jaw pinions and screws. The entire device is old, but works just fine (like it's owner ;-)
To the topic. The spindle is threaded 2 1/4" X 10 TPI.
Not 2 1/4 X 8 as is a common lathe configuration, and not 2 3/16 X 10 as is the Hardinge threaded spindle. I have chucks with both mentioned backing plates, and neither fits the dividing head. A quick look for commercial backing plates turned up no reference to the 2 1/4 X 10 configuration. Go figure!
The unique thread configuration sure complicates turning up an adaptor to fit either of the other two threads/
Sorry, no Deckel information, just what is going through at the moment.
CalG