Thanks for the info!Welcome to the Forum!
Well, it's not as collectable as you'd hope. For the most part,, all guns built by Ruger in 1976 have the "Made in the 200th year of American Liberty" markings.
And to get a premium,, (and usually a small premium for that model,) it would have to be New in Box with all the paperwork.
Price it as a shooter grade gun, since it's used,, and no box & papers.
In general,, the value would be in the $750-$850 range.