Here's the part I don't really understand. Are they marketing these as if they're coming from the original stadium? It's not clear, but one could get that impression. If this is part of the 2017 renovation, the brick in the north end zone hasn't been there since 1929. The certificate doesn't say that it's from the original stadium, it just says that it's an "authentic brick recovered from Kinnick Stadium during renovations in 2017". The whole thing is Kinnick Stadium, the old and the new, not just the original structure, so I would ask the question if you think you're buying something from 1929 - what part of the stadium is this brick coming from, if it matters to you. Calling it "authentic" isn't the same as saying it's from the original stadium.
BTW, I hate the renovation. It looks like a generic add-on to any stadium without regard to the rest of the stadium. At least when they did the south end zone, the matched the look.