Originally Posted by Clintopher
Was there and original before they started calling them MkI's?
Yes, there was. Sturm-Ruger's entry into the firearms business was with the pistol they called the Standard Model with a 4" barrel, looking much like a 4" Luger P-08. A few years later they came out with a target model they called the Mark I, with a 6" barrel with a deeply undercut front sight and micrometer adjustable rear sight (Micro, I think), and a better trigger/sear than the Standard Model.
spitfire-er is correct that the bolt is not locked back on an empty magazine, but can be manually locked back with the safety switch.
They were (and are) very rugged pistols. The only thing I have ever heard go wrong with one is the "ears" on the recoil spring guide are easily broken.
Field stripping is a little unusual, but not all that difficult once you have done it a few times, but detail stripping is a nightmare (for me, anyway), but unnecessary in normal use.
Ruger has a manual on-line in PDF format here: http://www.ruger-firearms.com/Firear...Manuals/48.pdf
The pistol is no longer in production, so the one you're looking at is worth whatever someone will pay for it, and that will depend on things beyond my knowledge -- like how badly you want it, and how badly the seller wants to get rid of it/need the cash?
The pistol has been "new and improved" twice, and the standard model has been out of production many years, now, for whatever that's worth in your negotiations.
The Old Guy