Thanks everyone, well for most of that anyway

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Looking more closely, it seems on the rather too roomy sx9s the buckle is a plate which has the surface texture and colour of stainless steel but I rather think it is tinned brass seeing a hint of copper colour along one edge. At least we wont' need HF rather than HCl to etch stainless chemically!! Actually they are a tidy 3" block heel and almost pass for a male style anyway.
The other pair has a three link chain for the buckle, the metal of which is tinny feeling and sounding. This metal might be a light alloy, a scrapping test feels harder than Al but softer than mild steel.
They have a thick sole, almost an inch, and a very broad splayed 4ins block heel. I'm a bit concerned the heel is too obvious and that they are rather too 'schoolgirl' like, although they are extremely close fitting, hold firm and are fun to walk in. I haven't decided yet if they are too small but, hey, it's only £4.99 at stake here!!!
ed:/ that is GBP4.99; do our north American friends see the UK pound sign properly on their screens?
/I