Yeah, about 1980 sounds right. Somewhere between 1979 and 1981 at the latest. After that, everybody went up to at least 16 channels. But 1979 was the first digital display programmables.
There are several good sources online for old scanner manuals. I like
www.bearcat1.com. And yes, they have the manual for your particular scanner. Also they consistently have the best new scanner prices on the net, hands down.
You paid about two to five times what that scanner is worth.