I am guessing mid to late 70's (the first 6 digits of the "code" stamped on the cowl of the engine is the date backwards (YY/MM/DD)
I used one similar for a while a few years back as a roughage mower, clocked up a lot of hours but eventually gave up mowing as a cashie business so it now resides behind my shed. It would no doubt still go with some petrol.
