Five (5X) plastic rear lens caps deepth are about 24mm for rangefinder Nikon S wide angle lenses.

for example, Nikon rangefinder lenses 28mm f/3.5, 35mm f/1.8 and 35mm f/2.5. Zeiss Contax rangefinder camera lenses  postwar Biogon 35mm f/2.8, Biogon 21mm f/4.5. Russia Kiev camera lenses. See the picture for detail.

It's a generic cover not made by Nikon. 

Good luck and thank you for bidding.