Best i can tell, they started making them in 1979, and came with Briggs, Tecumseh or a 'Deluxe Briggs"
www.tractordata.com
One that worries me, in the second pic, i see two holes to the right of the briggs sticker, on some of those briggs the model information and code was riveted to the blower housing. If it's not stamped above the spark plug or muffler.