I have seen several different heads for those microscopes,
but the Tc seems so be their only trinocular head with Siedentopf eye tubes.
While it appears similar to types T and F, as used with e.g. Labophots and Optiphots,
the Tc head imposes an additional 30mm of tube length.
It also differs by having its extension tube (AKA chimney) for photo relay lens secured to the head casting by 3 screws:
![Image](https://blekenbleu.github.io/microscope/Nikon/Trinoc/Tc.jpg)
... which are easily removed, with those chimney flange holes transferred to a 52-30mm step-down ring:
![Image](https://blekenbleu.github.io/microscope/Nikon/Trinoc/centered.jpg)
... then a 52-42mm step-up ring, M42 focusing helicoid and M42 mirrorless camera adapter
can yield parfocal direct projection:
![Image](https://blekenbleu.github.io/microscope/Nikon/Trinoc/ParfocalMetaphot.jpg)
Depending on the camera's flange to sensor distance, a different focusing helicoid may be wanted.
For example, 17-31mm helicoid works with 18mm flange distance and thin (2mm) M42 camera adapter,
but a 12-17mm or 10-15mm could work for longer flange distance and/or thicker adapter.