1959 - ⁠Leica Super Angulon 21mm f4

徠卡官方資料庫，序號 1645323 屬於 1959 年生產的 ⁠Leitz Super-Angulon 21mm f4 批次（該批次序號範圍為 1645301 至 1647000，總計僅 1,700 支）。這意味著它是在這款鏡頭問世的第二年製造的早期版本。 在 1950 年代末，徠卡雖然推出了 M 卡口系統，但市場上仍有大量使用巴納克螺口相機的愛好者。因此徠卡特別生產了原生 L39 螺口附帶的 M 轉接環的少量版本，出廠時直接幫這批 L39 版本的鏡頭鎖上了一個原廠 M 轉接環，將其作為「M 版本」銷售。因此鏡身有一個特殊的鎖定小螺絲，通常會有一顆極為微小的無頭固定螺絲。一旦解除這顆小螺絲，它就能現出 L39 的原形。 L39 版本在總產量中只佔了少數。

ACCORDING TO THE OFFICIAL LEICA DATABASE, THE SERIAL NUMBER 1645323 BELONGS TO A BATCH OF THE LEITZ SUPER-ANGULON 21MM F4 PRODUCED IN 1959 (THE SERIAL NUMBER RANGE FOR THIS BATCH IS 1645301 TO 1647000, WITH A TOTAL OF ONLY 1,700 UNITS). THIS MEANS IT IS AN EARLY VERSION MANUFACTURED IN THE SECOND YEAR OF THIS LENS'S RELEASE. IN THE LATE 1950S, ALTHOUGH LEICA HAD INTRODUCED THE M-MOUNT SYSTEM, THERE WAS STILL A LARGE NUMBER OF ENTHUSIASTS IN THE MARKET USING BARNACK SCREW-MOUNT CAMERAS. THEREFORE, LEICA SPECIALLY PRODUCED A SMALL NUMBER OF NATIVE L39 SCREW-MOUNT VERSIONS EQUIPPED WITH AN M-ADAPTER. FROM THE FACTORY, AN ORIGINAL M-ADAPTER WAS DIRECTLY SCREWED AND LOCKED ONTO THIS BATCH OF L39 LENSES, SELLING THEM AS THE "M VERSION." CONSEQUENTLY, THE LENS BODY FEATURES A SPECIAL LOCKING SCREW, USUALLY A TINY HEADLESS SET SCREW. ONCE THIS SMALL SCREW IS REMOVED, IT REVEALS ITS ORIGINAL L39 FORM. THE L39 VERSION ACCOUNTED FOR ONLY A SMALL FRACTION OF THE TOTAL PRODUCTION VOLUME.