Hello all three responders,
Thank you so very much for your expert and detailed replies.
I am so sorry I can't seem to post a picture here, but I think I've got the information I need from you regardless. (And my machine looks identical to the tan colored Viking in the post I linked in my first post.) Here is a link to just the picture of the machine from that post:
https://www.quiltingboard.com/attach...501_163233.jpg
I have a top-clamp machine, so thus it is probably pre-WWII. I think the 744 bobbins are probably the right ones. Thank you for the link, Rocsew.
The bobbin case looks just like the upper one in your photo, MacyBaby. Do you know if the beautiful Domestic machine you pictured takes a 744 bobbin? That would be the final proof, as your bobbin case is identical to mine.
Thank you all again for so much help.
Farmer Eric