Why both White Metal and A/A?

[peter4447]

Please forgive my ignorance over what is probably a simple matter but having been a member of this excellent site for a few months has encouraged me to start collecting badges to my old Regiment - The Green Howards.

Recently I purchased 2 Cap badges bearing the cypher and the XIX numeral that were introduced in the early 1970's (as per my avatar) when the Yorkshire Brigade badge was (thankfully) discontinued. Both have sliders and one is WM whilst the other is A/A. I seem to recall that when we (the 1st Bn) were issued with the 'new' badges we only received the 'staybrite' A/A version which we wore on all occasions in caps, side hats and berets. As I assume the WM versions with sliders are not officers' badges can anyone advise me please as to why a WM version of this badge was introduced?

Many thanks
Peter4447