Yes, we wore them as an alternative to the proper waistcoat. Unless you were Regt, or on a FJ sqn, in which case you wore aomething ostentatious. Tropical option for 5a, unless in 5b with the white waistoat?
With a DJ one dressed better ... hopefully! I have a large collection of DJ waistcoats that no longer fit, plus of course the black silk cummerbund. All down to the occasion, of course!
I still have mine. Offers over £5 will cover postage!