It's the freeze drain outlet of a LX LP300 spa pump whith the “M” mark for the old model which is nowhere to get. It won't get produced anymore and i managed to brake my original. So i measured the orginial and tried to recreate it. Even better because it has two barbs for catching the hose better.
Print it in 45 degrees in PETG or ABS.
The author marked this model as their own original creation.