Need help identifying foot part
 

What are these? 1/4"?, blind hem?, overcast foot?

They're Singer blind hem guides. You put them on with your zigzag foot.

One of these blind hem guides should been included with the Singer Fashion Mate 252 I purchased as a floor model in 1975.

One of our QB members was so kind to send me one each of the downward-attaching and backward-attaching blind hem guides which completed my"quest" to kit it out with everything that should have been "in the box."

Are any of your guides marked "Singer" and/or 161961?

No. No markings on either of them. Thank you for letting me know what they are. I'll have to give them a try. I am guessing they pair up with another foot?

I'll send a photo of the instructions page tomorrow.

You loosen or remove the General Purpose foot, slip the guide's U-shaped attachment point over the screw shank between the needle bar and the foot's attachment point. Tighten the General Purpose foot back in place. It will be lined up as shown on the picture above.