From the Buffalo Bill Center of the West, McCracken Research Library digital collection, WRA Co. drawing collection here are 2 versions of the same drawing showing details of a storage can for No. 4 or Mk V primers. The drawings are from Picatinny Arsenal, origin date is 1938 & show latter revisions.
Included in the pdf below is a screen shot of each drawing in its entirety and then screen shots of enlarged sections of each drawing to provide better detail.
What were these primers used in/for?