There will always be spurious iron spheroids out there. At the show I had a dealer honestly bring me a bunch of them from an historical society and I'd say fully a third were steel balls, but he sincerely wanted to confirm and not "pass the trash" There were some very good shot in there too which I appreciated getting the opportunity to put into my insatiable canister and grape stand rebuilding projects.
I also know some pre Civil War stuff has been replicated and disclosed as such (you can buy it now as new elsewhere online), but as it gets passed along sometimes the disclosures don't always stay with it and then it becomes a judgement call. Fortunately, Carl knows that stuff pretty well.