Welcome to AAPK.
1960s - Present is probably as close as you're going to be able to get, other than an educated guess from a Boker collector. As far as cleaning, at least get rid of the active rust. Scrubbing the rusty areas with a lead pencil should help some. If you're still not satisfied, the judicial use of 4-0 steel wool along with some Mothers Aluminum & Mag Polish (available at most automotive stores and probably Wal-Mart) should do the trick. Lots of folks on AAPK. Lots of different opinions and methods for dealing with the rust issue.
Left click on the image below to get a larger version. Click again if you cursor shows a circle with a plus sign in it.
I see Philip was typing at the same time as I was.
Forged on the anvil of discipline.
The Few. The Proud.
This country has become more about sub-groups than about it's unity as a nation.
"The #72 pattern has got to be pretty close to the perfect knife."
--T.J. Murphy 2012