FM S series economy version mag for 1 cyld Wisconsin. The Y number is Wisconsin part number for it and there is a chart listing magneto stuff at downloads at Wisconsin Motors dot com site will tell which ones it fits. Pretty common lots of them around and to be found on ebay and such so they don't bring too much sadly. S series FM mag has different coil so coil won't work in a FM J or X mag on welder engine either.
Looked other day. I got a new stock mag like that too with gear and some coils and grommets for cover for that mag. Still have some Wisconsin engines I use yet on roto tiller and a water pump those old engines will last forever.