Heat exchangers: original or SS?, How to pick one in the wild Options

[natemeins]

Hello all,
Forgive me if this has been asked already. I've recently acquired a set of heat exchangers from a popular auction site that were described as "little used, 1.7/1.8 heat exchangers". I got them for a steal. Upon receiving them, I realized they had very little rust, and we're in great condition. And by little rust, I mean no rust except for the muffler flanges which had little to moderate rust (looks like it may have been leaking for a while) The shrouds were "shiny" as if they were made of aluminum? And the headers are discolored with maybe light surface rust or something? Definately something a little polish or scouring pad could clean and make shiny again.  I checked it with a fridge magnet and the shroud was non-ferrous, and the headers barely if anything had any magnetism. Have I stumbled upon a set of well-used stainless heat exchangers or just a damn good set of originals? Is there a better tell like a stamping or something?

[McMark]

My question still stands: is there any way to verify HE's are SS in the wild?

It's a pretty safe bet that if you see shiny or silver metal, they are SSI (the only SS heat exchangers). If you see black or rusty, they're stock. Late model 180° exhaust excluded.