If it has a Briggs and Stratton engine, as most of them seem to, it will have Model, Type and Code stamped on it somewhere - probably on the cooling air cowl. That will tell us the date of manufacture of the engine, which will help with identifying the rest of the machine. The serial number beginning with a letter instead of a number suggests it is relatively recent. Here is a service bulletin explaining which transmissions they used and how their serial numbers worked:
[Linked Image]

I'm guessing your machine may have been made in or after the year 2000, to have that A prefix.