The headstamp reads: “F.S.C. 12-41 1.10 MkI 75cal anchor R.R.A.”. This headstamp came up before viewtopic.php?f=1&t=6947 but Falcon did not get info he wanted. Let me try one more time. What is FSC? What is RRA? If the caliber is given as 1.1 inch, why is 75cal there?
“75” is the barrel length in calibers - a usual designation practice in the artillery sphere. In the rest of the world often designated as L/75 then.
Some other countries (including German navy in WWII) even gave caliber lengths for projectiles.
Vlad, the case was made by Florence Stove Co. of Kankakee, Illinois and the primer by Triumph Explosives, Inc. of Elkton, Maryland.
Note: The manufacturer of this case was previously discussed in this thread iaaforum.org/forum3/viewtopi … =8&t=14571, but none the two companies mentioned are correct. The same applies to 20 and 40 mm cases.