These were not made by MTD. The ST Series lawn tractors were built in house by Bolens from 1984 through the mid 90's, with the later models marketed under the Troybilt brand. They were discontinued and replaced with the Troybilt LTX Series in 96 or 97. Troybilt contracted with MTD for some stamping operations for the LTX tractors when the Bolens plant in Port Washington was closed.That is a bolens st 125 made in 1986. They came with a 12.5 hp briggs i/c engine I do believe they were made by mtd. The name 'Bolens' was carried by mtd until 2010. This is all i know.