As with many folks here sometimes it is hard to distinguish whether that silvery metal is stainless steel or aluminum after you have done the magnet test. As we all know stainless throws a spark while aluminum does not. I found a cheap tool at Harbor Freight you might want to think about. It is a Rotary Tool Set. Basically a small high speed drill, and there is a bunch of attachments for it, including small thin cutoff wheels. This can be used to do the spark test, without lugging a cumbersome angle grinder around. It has many other wheels too, so can be used for many other things. The cost is $10.99, and if you have a 20% off coupon then it is less than 10 bucks, and that is including tax.