Stainless as a one-colour, mono-tone, consistant silver colour. Tin plated has a patchy, non-consistant colour to it. I gotta check if my 30 qt s/s/ bowl is magnetic, tin plated steel definately is
It's easy to gougea bowl, drop something hard and metalic in the bowl, and let 'er rip.
The bowls are expensive, but you can be, uhh, "creative" about asking for a new one.
Love the 60 qts, but they are big. You can get a "reducing collar" that will accept a 40, 30, or 20 qt bowl, on a 60 qt mixer, but you also have to get the appropriate "reduced" agitator (paddle whip, etc) as well.. Most bakery supply places have these, and usually they are used and a bit cheaper. Two bowls can be very helpful in a fast paced kitchen--almost, but not quite, like having two mixers
S/S will rust if metal particles are imbedded in it--like steel wool or steel scrubbie strands imbedded in a fresh gouge. Get yourself a Dremel tool and some Jewler's rouge and polish up the gouge.
If the bowl is tin plated steel, the gouge will allways rust, like 5 minutes after washing it. All you can do is wipe on a little oil and wipe off the rust.