I don't think that a gearcase would suffer problems if a 'detergent' oil caused crud to come loose. The odd thing is that modern reports suggest that while detergent oils keep particles in suspension, they don't actually clean old oil deposits. Maybe that's because there have been no true 'straight' oils for seventy-five years and actually the early detergents did have a cleaning action ?
Colour coding seems to have been likely with workshop 1/2 pint cans and the need is obvious but less so with a single can carried by a motorcyclist. I suspect that the pre-war cans were finished in aluminium paint which became unavailable so a copper metallic was substituted and then finally the mustard straight colour which was on the last of the brass cap and all of the steel pressed cap 200 Wescos.
The great puzzle for me remains how they could have expected C600 oil to stay in a Tecalemeit grease gun (no seals and no cap). They were grease guns...
Was C600 rated at 600 centistokes or was the numbering coincidental ?
Well, if the only gain I get from this thread is the fact that the nipples didn't have a spring and ball I shall be happy! Mine don't and after the misery of finding a complete set of them and having them chromed, I'd have been very upset I'd gotten it wrong. ! Phew!!