Some good closeup pictures of the damaged portions and I can probably tell you if it's stainless or not.

Try the magnet test first, but as Tim noted some stainless is magnetic or mildly magnetic, still worth trying.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-