here is where to find the build date of your machine via the serial number
https://ismacs.net/singer_sewing_mac...-database.html
the K may mean it was built at the Scotland factory
google brings back some general results with the number 96K-41
I've found singer manuals were pretty generic for my needs, but eventually found the originals with a search watch on ebay.
Good luck with your machine! and 40 years isn't very old
I have shirts older than that