Very early British screw-in primers?

[Darkman]

I recently picked up these very early (c. 1880s-1890s?) screw in primers stamped RL (Mk) II and RL (Mk) III. Both are missing caps but have 3 flash holes into a powder magazine, and both have 1/2” x 14 TPI right hand threads.
I haven’t been able to locate any documentation on them. Would anyone know what cases they are for?
Thanks, Graeme

 

[Burney Davis]

They aren't primers Graeme, they are a type of gaine/exploder typically used in the 12pr/15pr Boer War era shapnel shells under the fuze. There are a number of different variations. Picture of one in situ on a 15pr below.

 

[Darkman]

Ah OK, thanks Darrel. Haven’t seen one before. I have a few 15 Prs, but none have this exploder thingy fitted. Presumably the flash tube pushed into it.

 

[Burney Davis]

The pictures below is of the internals of an early 5 in BL shrapnel shell showing the flash tube arrangement. They were generally used under the 50/60 series of fuzes.