That roundel was also somewhat larger than normal. The black chassis would have been a one-off, as this was an experimental livery. In the same way, the very first half doizen or so coaches to get black'n'tan had one-off differences, like numbers in different positions, and non-standard fonts.
In the early 1970s, I believe that consideration was given to painting goods wagons a sort of beige-y "desert sand" colour, instead of brown, like Dublin buses. But it was not proceeded with, and I am unaware even of an experimental paint job being done.
The CIE roundel with tan surround, as opposed to white, was as far as I am aware confined to new vans - namely "H"'s and "Palvans". All older vans, all open wagons, plus SOME "H"s, had all-white roundels. I never saw a palvan with a white roundel, but it's at least theoretically possible.
All logos on all brown-painted wagons were always white. Some got discoloured with age and brake dust, but all were white initially.
Very few wagons ever got the "set-of-points" logo after CIE became IE. The few that did tended to be departmental stock. Ordinary wagons - IF repainted - just had the numbers, no logo.