[badjez]

"I am told that these were also worn by the VTC in all black and only the swan necked type are genuine and swapped to BM Sphinx badges in 1919."

Unless there is photographic evidence of this I'd take it with a pinch of salt. Prior to the VTC receiving War Office recognition (on 19.04.16.) the War Office were very adamant that the VTC would not wear any item of uniform or insignia pertinent to units of the Army. I cannot see any TF Association permitting their regimental cap badges to be worn by VTC units. Post 1916 the only authorised cap badge for the ex-VTC units were the universal Royal Arms.
All Volunteers were authorised for disbandment on 25.09.19.

Regarding the all brass badge, I've never seen one, but a brass badge did appear in an on-line auction in 2006. It is impossible to ascertain the authenticity of this badge. Pictures attached (downloaded from web- copywrite unknown). I've never found reference to an economy version in the Pimlico ledgers stored at Kew.

Crown Imperial issue 95 (Summer 1995) has a letter claiming that this badge, with slider, is the pre 1948 OSD collar badge. Again, no evidence was produced to support this assertion. Colin Churchill's book does not mention a collar badge with slider.

Stephen.