Assuming that is the rear of a Bridgeport type turret mill…there were a couple of attachments that fitted. 1) a slotting head 2) a cherrying head which cuts woodruff key slots. I think those are the correct names.
Yes rear of series 1. I'll have to search for some pictures.
diyengineer
The the slotter was the most used of the 2, the Cherrying Head was used for mold making, if your machine is set up as a CNC, then they would be a real pain, to unplug everything, then turn the turret 180 deg to use it, they were mainly used on manual machine, there are many other attachments for the Bridgeport head
Mactec54
Oh that's cool. Seems like it's a real work horse with a ton of options. I can see why they are so popular, not just quality but the ability to expand also.