I'm finding more & more Aluminum wire in the microwave transformers.
Out of the last three that I scrapped, two of them had 1 of the 2 coils in the transformer made from Ali.

Any silver/stainless steel microwave I'd suspect has at least 1 coil made from Ali, maybe both made of Ali.
Yah have to check them by scrapeing them. Silver = Ali wire, they always have a gold/copper coloured varnish painted on them too.