Cute PJs and machines - are they models 15-91 and 221 (Featherweight)?
My daughter just purchased a 15-91 at an estate sale while looking for a copy of my 221. I have been trying to get a feel for the size of her machine and your photo is really a good size comparison of the machines.
Did you know - all of the attachments for your 15-91 will work on the 221 (since they are both low shank machines). Only thing different is the bobbin (which is NOT interchangeable). I found this out today at our guild biannual quilt show - one of the vendors specializes in old singer attachments. I was looking for attachments for my daughters machine.
Congrats on your find!