I have a used Ruger MK1 in very good condition it was Introduced in 1950, the MK I Target model was basically the same as the Standard pistol, except that it boasted a 6.875-inch (17.46 cm) barrel, adjustable target style trigger, a "Micro" adjustable rear sight, and a front sight blade undercut to reduce glare.[2] In 1952, a 5.25-inch (13.3 cm) barreled version of the MK I Target was added to the lineup, but manufactured only through 1957, making it a collectible rarity today.[2] A 5.5-inch (14 cm) heavy bull barreled version of the MK I Target became available in 1963, eventually becoming the most popular length for Ruger Target MK pistols.[2] Like their Standard model brethren, target models underwent the A 100 grip frame redesign in 1971