Based on notes on the web, it is probably from between 1981 and mid 80's.

I am having troubles deciding if that is original or an older restoration.

Does "Colnago" on the downtube and seattube appear to be painted on or a decal?

As I understand it, COVID is turning the bike market upside-down. I see quite a few people asking for > $1000 for frames on E-Bay, but I think the ones that are selling are going for closer to $400 to $600.

By the mid 80's, there were quite a few better Colnago bikes available.