I think there is alot of misinformation about stainless steel on this forum. Some stainless steels are magnetic, some aren't. It has nothing to do with it's quality. You must use the proper grade of stainless for the particular application. For example, some 400 grades of martensitic stainless have a higher carbon content for a reason, it makes them amenable to quench and temper heat treatment to produce high levels of strength and hardness. Just because it's magnetic does not make it inferior stainless. As I said, it is more important to use the proper grade for your application. As for identifying a particular grade of stainless without chemical analysis, you may be reduced to a spark test with a grinder. The simplest way to do this is to compare the sparks from a known piece of steel to the sparks from your part. This something of a forgotten art, but if you are good at it, it is effective.