 The Standard model was under constant production in basically the same form for the next 33 years, but the new corporation expanded the basic Standard archetype into a product line of pistols over time by the introduction of a number of variant models.These took the form of offering additional barrel lengths and configurations, creating versions optimized for target shooting, and adding the finish option of stainless steel.The line was also refined with three mechanical “MK” series upgrades, the Mk II, Mk III and Mk IV, in 1982, 2004 and 2016 The MK II added a slide stop that held the slide open on the last round, and also was available in stainless steel.