Thank you. Actually, videos cannot be posted on Quilting Board. However, links to videos can be posted.
You have what is considered a Japenese 15 clone machine. You can read about them at
Will the Real 15 clone please stand up There are some pictures of actual Singer sewing machines that they were modeled after. It may or may not have a JA or JC and then a number somewhere on the machine. To read about what those numbers mean there is a page that explains a little about them with a list at
http://www.doubleveil.net/zssmp/resources.htm#jajc
You have a "Greist" manual for the attachments. There is a pdf of that manual at
https://www.sil.si.edu/DigitalCollec.../sil10-215.pdf Greist was manufacturer of sewing machine attachments for many years and many different companies including Singer.
It looks like you may have gotten a round stretch belt. Most of the vintage machine enthusiasts suggest not using a round stretch belt. One person indicated that "The stretch o-ring belts wear out the motor bearings." There is a pdf for belt size and install at
https://web.archive.org/web/20160317...%20install.pdf Unfortunately, sew-classic is no longer in business. There are also instructions
TO REGULATE BELT TENSION on the MOTOR:
at
https://sewingmachine221sale.bizland...re/page90.html
There is a generic manual for this type of machine at
https://ismacs.net/singer_sewing_mac...ion-manual.pdf
You can make the pictures a little larger. They just need to be under 2MB. Would like to see the front of the machine.