"Aluminium die cast piston drawn in lieu of steel piston" means that the alloy piston is "in the place of" the steel one. To me, that means the alloy one replaced the steel one (and not implying they included the drawing for the alloy one because they didn't have a drawing for the steel one).

There was a post on Ausmini that I cannot find in "Search" in which John Smidt commented on the alternative materials. He may have commented on the change point.

This one?

viewtopic.php?f=2&t=84897&p=935003

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

Yes, Winabbey, that's the post I couldn't find.... hiding in plain sight.

I interpreted the other way, that the drawing still shows the alloy piston instead of the 'new' steel one, perhaps to save drawing office time as there isn't much difference, but I guess it could be either.

The drawing for the actual piston, if we could find it, would show the material used and the change point.

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ex-NSW Police 1970 MK II Cooper S
VMCI #43

my mind mostly...

I have a big pile of bags (I counted 20 odd last year when looking for a good one), I've didn't notice if there was a different piston, but I didn't look either. There ought to be a couple of steel ones in there somewhere.

I would have loved to see a drawing of the "special" longer version, if there was a part number I'd start searching for a pair but I doubt I'd find some. When I get excited enough I'll make some

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did I tell you that I won a trophy?