early british unidentified double ended plug/object

[Dodgy Dougal]

I've recently acquired two of whatever these are from a good lad on this forum, both different sizes height wise but both have the same thread size. here are photographs of just one. Another collector on here has what appears to be the top half of the same item thats been aggressively sheered off. does anyone have any guesses for what it could be? it could be something that holds two halves of something ordnance together, perhaps two halves of a projectile, or for a sabot to be affixed to the base of something early? on the longer end below the centre brass section there is a bevel so it screws into something.

 

[Millsman]

Normally the brass pieces with the square hole are transit plugs for shells. I've never seen one with two opposing threads. Royal Laboratories made so must be some ordnance.