Welcome to the group Ken.
Your tractor is called a Handiman. It was built in 1957, and is from the second yr of production for these machine. Yours and another(917.60115 a 110V start) were followed by several other models up into the early 60's when they finally stopped making walk-behinds. You should have a tag on the tiller unit and the counterweight sitting on top of it. Its pretty common for the tags to go missing.
Tractor using the number 917.57xxx are the post war bullet nosed ones, TriTrac's used 917.59xxx. The early suburban line used the 917.60xxx numbers also but they start in the 600's, where yours starts in the 100's. There is no way to get a model yr exactly from a DB
number. They had about 3 differnt systems to id the tractor. There is the tractors number on the tag, the catalog number found when ordering it, and a bundle number that the factory used to id the units. None of these make any sence, as all are differant. You have to have all the catologs and models numbers together and take several yrs of free time to try and make it all work out. Luck would have it that several of us DB
collectors have been doing it for about 20yrs now, and still arent done.