This part is a Filter Cartridge Wall Fitting Mount, 1 1/2" SAE Acme Female Pipe Thread X 1 1/2" Slip, 2 1/8" Hole Size.
This fitting would measure about 1 5/8-1 7/8 across the threads and features a 1 1/2" Slip glue in fitting on the bottom that would receive 1 1/2" pipe or fitting that would measure about 1 7/8" OD..
The Hole Size in the shell of the tub would be about 2-1/8"...
One of the filters that would fit this would be here: 1 1/2" SAE Thread Filter..
