This is great! I loved my Kenmore and I really think it's still somewhere in the basement, although we haven't been able to find it. (The hot water hose to the washer burst a few years ago when we were out of town and some things went when they did the cleanup - still not organized.) You have a wonderful assortment of cams. I have the same buttonholer, but got it after I lost the machine and can't figure out how it should work.
I'm guessing that the S M L dial is for the stitch length (since it says Length Modifier), maybe for Short, Medium and Long.
Etsy has some manuals.
Hope you have lots of fun with all the accessories!