Ruger's first .22 caliber model was the Mark I, invented about 1949, and at the time it went for $39.95. It was their first gun ever, and they employed a few cost-cutting manufacturing practices such as a heavy-duty pressing methods that would create the frame from sheet metal, and the receiver is made from high-quality steel tubing.
When Ruger went from the Mark I to the Mark II, there weren't many differences but there were more models to choose from. But it's the difference between the Mark II and the newer Mark III that is significant, presenting different pros for dealers who want to own either model.
(MkIII Standard, Image by Ruger)
The Mark III began production in 2004 and is still produced today as one of Ruger's more popular products. It's similar to its predecessors the Mark I and the Mark II-- though it has several differences. The primary differences are the loaded chamber indicator, more popular push-button-style magazine release (the Mark I and the Mark II have heel-clip magazine releases), and it has a magazine disconnect safety which prevents the gun from being fired without the magazine being inserted.
Some of these differences were choices that the Ruger company chose to make so that the Mark III could be sold in California. Now California mandates that all pistols have to have a loaded chamber indicator and a magazine disconnect safety. Also semiautomatic handguns introduced in recent months now have to be microstamp compliant, which is a whole different ball of wax.
(MkIII with fluted barrel and target grips. Photo credit: Ruger)
Another great difference is the magazine release. The Mark I and the Mark II were both models that operated with a heel-clip magazine release, but American shooters have grown to expect push-button magazine releases in their self-loading pistols. It is for these customers that Ruger changed the magazine release for the Mark III.
The Mark III is offered in several other versions than the Mark I and the Mark II. The Mark I was offered in two models: standard or target. The Mark II was offered in: standard, target, bull-barreled, stainless steel models, and a few other optional differences. The Mark III now is available in tapered, bull-barreled, fluted, short, long, threaded, and other barrel choices. It's also available in standard, target, and hunting-specific models.
Another interesting version of the Mark models (starting all the way back as Mark II), is the .22/.45. These polymer-grip frames are angled differently, so that the handle resembles more the 1911 government model .45 caliber handgun. Some of the Mark III versions provide the user the opportunity to remove the grip panels, but the primary feature here is comfort, intended to appeal to users who have had military service or are familiar with the grip handle of the 1911 pistol. Replacement grip panels for all of the Marks are available factory-direct from Ruger or from numerous after-market suppliers, some of which include exotic materials such as stag-horn, rams-horn, and exotic woods.
In days past, ivory would have been offered, but now these materials offer very appealing looks.
Additionally, the Mark III threaded muzzles can accept suppressors and flash-hiders. Some are even equipped from the factory with flash-hiders.
The Mark model was the first .22 caliber gun that Ruger ever made, and though you may choose to purchase a newer Mark III model, you are still handling a model derived from the original Mark. It has a grand heritage linking back to Bill Ruger's original design, though it has a few contemporary features that make it worthwhile.