whats this interesting item

[wrecker]

Hi all,
i got this in with some items of militaria,the box colour suggests air ministry or naval.
Box is very well made and has M28 No2 scratced in the top and stamped exr23,inside lid is stencil M28 and written in pen E6H5901,rate book section 5B.
main tool has knurled handle and stamped EXTR 23 JKA 73,it has two removable knurled pins and a round part with a hole that the small pins fitted in box go into and are adjusted by spanner which is stamped JKA 78.
All top quality stuff,but whats it for,over to you.........

[operaman]

My wifes vibebrator

[SteveR]

Short arm inspection kit.