This is a low profile, 2" threaded visual adapter for use with the former style SVQ100 astrograph which used the 3" Feather Touch rotating focuser. In this model the entire focuser rotated relative to the main tube. This low profile adapter is made for this former model.
The newer version of the SVQ100 has the rotator located behind the focuser and tube.
This adapter threads directly into the Feather Touch 3" focuser draw tube and accommodates 2" accessories using a compression ring clamp.
The images below show this adapter on the 3" rotating Feather Touch focuser.