I studied these hypos extensively for an SDStudios replica some years ago. I actually identified three variations: from top, season 1, season 2, and a hybrid version that appears in a few episodes (Patterns of Force being one, if I recall)
Note that the season 1 injector tip is designed differently, with a split "tongue." Also the finger guard is cosdiderably shorter. The medicine vial fits down father into the tube on the later season version.
Yes... I realized how bad my first attempt was. I teamed up with a 3d artist and found a CNC shop to help with the project.. here is the new 100% screen accurate season 2 we have come up with.. completely field strip-able made from measurements of the actual screen used prop
Still needs to be finished and polished... now working on a perfect season 1