Vac_Whisperer,
Since time has expired for me to edit my posts, I need to make the following corrections:
When the Dual Sanitronic 50 came out in 1965, the existing universal coupler design was given a protruding tab located close to the right attaching lug, so as to trip the 2nd button of the newly-designed safety switch (2nd being high speed for hose use). The Crystalator was also given the same protruding tab for the same reason. Therefore, you can identify which of these is for the Sanitronic VII and which are for the D50. The lack of the tab by the right attaching lug would mean the hose and Crystalator was designed only for the VII.
Later on, the universal coupler and Crystalator (w/o the protrusion for the high speed mode) would be replaced by equivalents with the protruding tab by the right attaching lug.
~Ben