This magazine is produced by Walther in 1940 for an "ac40 date added variation". These pistols have the number 40 engraved below the ac marking on the slide. The serial numbers for this pistol variation ranges from approximately 9950 to 5900a.
Three magazine variations can be found in this serial number range. The 1st variation of these magazines were issued with pistols up to about serial number 4400a and are the same as the previous 480 and ac-no-date variations, except a P.38 is stamped on the left side above the serial number. From this point on all Walther magazines were stamped with the P.38 marking.
The a-suffix of the serial number was not used on this magazine variation. Below is a magazine with serial number 3428 and this magazine belongs to an ac-date-added variation with serial number 3428a. It has two side by side E/359 inspection stamps on the spine and the small parts are also stamped with E/359.