Hello,
If the engine cowling is original then there should be the Model, Type and Code numbers stamped into it...they may be on the top or on the flat vertical side that faces the carb/airfilter.?
Sometimes some detective work is needed if much paint has been added or if rust has wormed its way in...perhaps tracing paper and pencil job.?
The first set of numbers give the engine size, build and fitments..I couldn't do that without a guide ref
But the last set, Code, are the ones that give the date of engine build...Year, Month, Day, Factory....
The numbers give all the answers ref spare parts ..and ability to get a parts diagram/list download...and perhaps a representative operating manual.(not repair manual) from;
http://www2.briggsandstratton.com/maint_repair/manual_and_more/index.aspx?buyOnce on the parts page you will see a range of exhaust mufflers to suit the engine in different applications....most garden machinery agents will stock a certain selection...a clue to prices might come from here;
http://www.briggsbits.co.uk/I think it looks at least 7hp?? maybe 8hp.??
There looks some paint and corrosion ..but hope you can find the numbers
All the best,
"Dori"