Telling aluminum from stainless steel?

[lobadobadingdong]

put it in a microwave and turn on the microwave, if the microwave explodes then it's aluminum.

 

[Squisher]

Like others have said stainless can be magnetic or not. 300 series stainless is not 400 series has chromium and is magnetic(but only 50% as much as 10 series steel).

Try scratching it, if the exposed metal is really shinny at first but dulls within the hour it's Al.

You could try sparking it with a grinding wheel all stainless gives out a small yellow spark, Al none.

 

[XZeroII]

Buy a new one that you know what it is.