Yep, I looked closer.
The light is definitely red - just because it is natural light doesn't mean it is neutral. Being late in the day makes it even redder. Take my word as a photographer of many years' experience, the lighting is red, which affects the colour. I've taken the liberty of colour correcting two of the pics - still not perfect, but a lot closer to natural (as can be seen by the grey of the bare metal brackets and the black of the oil cap).
The second rocker cover, which you say is gold, looks very green, particularly at the bottom, where it may be slightly in the shadow. the third rocker cover looks more gold.
The Cooper S block (sorry I didn't pick up on that - my bad) looks very green now!
So, what is the bottom cover from? - the one with the Aussie MOWOG stamped in it.
While the 998cc engines were apparently assembled in Australia, it was not until the Mini K, when the marketing department wanted to make more of a point of the Australian content, that the rocker covers received the stamping of the map with MOWOG across it.
So, it seems that the gold rocker cover is from a Mini K, Mini 1100 or Morris 1100, the middle rocker cover is from almost any engine from 1965 to 1969 and the top one is from an 850 - of course they could be from anything these days - easy to change.
All this supports what I've already been saying, so thanks for that.
Cheers,
Watto.