Your machine is older than mine as my patent dates run from Jan 18.87 through May 26.96. The pictures look exactly like mine except mine has a spring belt. There are no markings on the bobbin case. All attachments were made by Greist.
I am overdue for a visit to a gentleman I know that has been selling and repairing sewing machines for over 60 years. He is 85 years old and still goes to work 6 days a week. Anyway, I will drop in on him to see if he can give me any info that I can pass along to you.
I enjoy the challenge of getting an old machine up and running but usually try to stick with ones that all the parts are there. You are much braver than I am.