Frequently, when we get these old machines there are parts and manuals that come with them that do
not have anything to do with the machine. If the slide plates go from front to back it would be a 27. If the bobbin cover is on the side, it is probably a 15 or 66.
I'm going to guess that the machine you have is probably a 27 and is a long shuttle like Tartan's. There are many manuals for these machines on the internet. One of which can be found at
https://www.sil.si.edu/DigitalCollec...0673/index.htm the instructions and what came in the "puzzle box" of attachments can be found at
https://www.sil.si.edu/DigitalCollec...0675/index.htm There others and some are in pdf form.
Looking forward to seeing a picture of your machine and serial number.
Janey - Neat people never make the exciting discoveries I do.