Hi Harris,
The 45 you've picked up there is a Series II Twin Railer and it would've been manufactured somewhere around later 1972 into 73.
As this was a Kirby powered unit they can not be accurately dated as with the Briggs powered machines they can be dated via the engine. Kirby's didn't have a date encrypted within any numbering on the unit.
Depending on what you intend doing with this mower is very dependant on what advise we'd give you. One things for sure and that is I'm sure this machine will have fractured rails underneath that engine.
Regardless of that if you are in this for the long haul then I'd hoik the old Kirby off and refit with a new generation Briggs power plant. The Series II machines are on borrowed time if they are powered by one of the older engines as they induce way too much thump into the chassis while the new engines are far kinder on these ol' girls.
Cheers,
BB.
