Welcome to MLF!! 
Nice Briggs engine you have there. Briggs actually has most of their original manuals that you can download directly from their site.
Small Engine Manuals | Lawn Mower Manuals | Briggs & Stratton
Regarding the year of it, you should be able to look it up here on the ASECC site via their number charts.
A.S.E.C.C.`s Briggs & Stratton Technical Data
Nice Briggs engine you have there. Briggs actually has most of their original manuals that you can download directly from their site.
Small Engine Manuals | Lawn Mower Manuals | Briggs & Stratton
Regarding the year of it, you should be able to look it up here on the ASECC site via their number charts.
A.S.E.C.C.`s Briggs & Stratton Technical Data