[johnG]

I cannot comment on the formation sign itself, but perhaps what I have to say might have some bearing on the question.

I knew of the 1st Regt. H.A.c. when, if memory serves me right, they were

1st Regt HAC (IIth Regt RHA)

To my mind that makes them HAC, and that is the correct shoulder title, BUT
just a few years ago on Waterloo Station, London I saw a chap wearing an HAC necktie and commented on it, only for him to abruptly tell me he was 'The 11th'



This leads me to think that although HAC would be the correct shoulder title here, there were individuals who were so proud of their RHA connection (and why not), that as a matter of preference they put up RHA instead of HAC.

Now having slung a grenade into the mix I will put on my tin foil hat and retire to a safe distance.

Edited to add: How about an RHA man attached to HAC - just to keep their minds off the joys of the Sutling Room back home, and being of the same group would have worn the same formation sign, but s/t's of his own regiment.

johnG