Helen Scarth wrote:

Could someone please have a look at this picture -
http://www.treadles.ca/website/plate.jpg and see if they can tell if
it's brass plating over steel/nickel/whatever, or vice versa. One
word of warning though, the picture is 381K in size.

It's a slide plate from an 1870 Singer sewing machine and I'm
intrigued about it because earlier machines had what I'd assumed to be
solid brass plates until this one appeared with the two colours.

I've tried scratching it with a pin, sliding my fingernail across the
two colours and checked it with a 30 power magnifying glass, all with
inconclusive results.

Hopefully someone here will have far more knowledge of metallurgy and
better eyes than I do. Larger scans available on request.

Helen
well looking at it: reminds me of one of my old BRASS cashregisters.. it
is solid brass with a chrome/ or nickle plating that just about all came
off... and someone painted the brass and the parts of nickle that were
still there with a guilt paint in the 1930's or there after.. take one
edge and rub it on a stone(sharpening stone) and see if you get brass on
the stone... i cant think of what chemical you can use to then put on
the scraping on the stone(but it should change colors when you do...
some kind of acid... or take it with you to an aluminun recycling
centerr and they are not busy the guy might check it for you.. look for
the silver stuff on the part and see how it flakes up... with long
fingernail see if you can lift it up.. is it silver paint or metal???
chrome/nickle plating????/