I'm not an expert on the No. 1, but my gunsmith is. He tells me the very earliest No. 1s, which have the breech blocks serial numbered to the rifle, are some of the best guns ever to come out of an American factory. I *think* they were made in the late 60s.
Ruger used subcontracted barrels in those days, which sometimes shoot and sometimes won't. My gunsmith said they were "the best $7 barrels in the world," which is NOT a compliment. What made the early guns so much better is the degree of finish work. They were hand-fitted, and the parts were very nicely finished. The stocks were also hand-finished. Triggers were better, too.
So, if you want a really nicely-finished one, look for an early one. But, you can't count on it being a good shooter. I'm hunting for an early numbered-block gun myself, and I'm planning on having it rebarrelled with a Wells cut-rifled barrel in .303 British. I'll see how it shoots and, if necessary, have a set-screw added to the forearm hanger. It should be a fun project.
Best,
Joe