Ruger pistol magazines have evolved over the 60 or so years since the first RST4 was introduced in 1949. Here is some help in identifying these magazines:
1) Was used on the early RST4, RST6 and Mark I pistols with what's cataloged as the A54 frames. The follower slot exists only on the right side of the magazine. Follower button diameter is .250 diameter. These magazines have a solid, non-removable bottom and hold 9-rounds.
2) In mid-1971 the A100 grip frames were introduced. Magazine bodies have follower slots on both sides of the magazine, so the follower button can be switched over to the right side and used in the A54 frame pistols. The solid base-plate remains and capacity is still 9-rounds.
3) This is what the *NEW* replacement magazines look like when you order a replacement for #1 and #2. Follower slots on both sides, but this magazine now has a removeable base plate for easier cleaning. The magazine body is the same as the Mark II style magazines.
4) Early Mark II magazines have the .250 diameter follower button on the left side of the magazine. Here again, follower slots are on both sides and most often these magazines will work in the early pistols when the follower button is moved to the appropriate side. Capacity in these magazines is now 10 rounds.
5) This is the later style of Mark II magazine having the larger (.327 diameter) follower button that started when production of the Mark pistols was moved to the Prescott, AZ facility. These magazines can also be adapted to the early pistols. Capacity remains at 10-rounds
6) Here is the magazine currently sold as *NEW* replacement magazines for Mark II pistols when you order a new magazine. These magazines use the "three-ring" style of follower that's being used on all magazines hereafter. These will also work on the early pistols. Capacity again, is 10-rounds
7) This is a Mark III style of magazine that features the "notch" on the right side of the magazine body for the 1911 style magazine release. The notch on the left side of the magazine corresponds with a "nub" on the trigger that when pulled will verify that the magazine has been seated into the grip frame securely.
8) This magazine is unique to and will only work in the 22/45 style of pistol due to the floor-plate being used. The magazine body is the same as the Mark III style in all other ways.
1) Base plates on the early magazines are fixed in position and are non-removable. To remove the follower, it must be done from the top of the magazine.
2) The base plate on the *NEW* replacement magazines for the early pistols resembles a Mark II magazine base plate but is silver gray in color, with the red background behind a gray eagle. The emblem now just has the "R" for Ruger only, with the "S" for Sturm being removed.
3) With the introduction of the Mark II pistols, we saee a silver eagle with a black background on the removeable base plate.
4) After Rugers 50th anniversary (1999) the background for the silver eagle went from black to red.
5) On all current magazines, those provided with new pistols and magazines sold as replacements, the floorplate logo are all black. You'll also notice that the logo has been rotated 180-degrees in position and the "R" is the only letter in the logo.
6) The Ruger Mark 22/45 pistols have a unique floorplate shape that only works on the "kydex" frame style pistols.
1) This follower is what's used in the early magazines. The follower is made of "pot" metal, most likely zinc.
2) The black plastic follower made it's debut during the transition to the Mark II pistols. This follower is used in all the magazines that arrive with new Mark pistols with 10-round magazines.
3) The silver gray follower is matched with a like colored base involved with the replacement 9-round magazines for the early pistols. These followeres can easily be trimmed at the cylinder for the follower spring to make it a 10-round magazine.