Check out the OP Ken. The S/N plate was in one of the photos - 85J7054.
To the OP. Maybe a bit of clarification is required when talking about manuals, to give you an idea of what you are looking at when you see stuff advertised online in places like Ebay.
Starting from the cheapest they are: -
1. Operation & Maintenance. The buff-colour book that should live in the pocket in the back of the seat but in your case probably disappeared long ago. Price about $50.
2. Parts Manual. Not necessarily a "must have" but if you get into all sorts of repairs it might be handy to have one. Price less than $100.
3. Service Manual. Contains the "how to" regarding Disassembly & Assembly, Testing & Adjusting, Specifications, Electrical Schematic and a lot more besides. The paper versions of the Service Manual used to also contain a copy of the O&M Manual.
A comment. When I look at Parts & Service information online for this machine the system asks me to choose am I looking at the machine or at the engine. That leads me to believe that (as old-school manuals used to be) there will be no engine information in the Service Manual. if that is true it might require separate Parts & Service Manuals for the engine.
All are available here either in CD or in paper form -
https://www.servicemanualpro.com/?page=Products&searchbox=85J07054
This one is typical of what I was talking about but it is for a slighlty higher series of 85J machine than yours -
https://www.ebay.com/c/1734121376