[drcy]

I shy away from the term "forensic analysis" as bad autograph "authenticators'" at places like Coaches Corner have given "forensic" a bad connotation in the hobby.

My areas of expertise are ink-and-printing press prints and photographs. Especially with old photographs, I (and everyone else) will have no idea who is in the photo or where it came from. I determine that they are original (or fake or reprint) by examining the physical photograph itself . . . And no one is omniscient and sometimes I don't know.

So saying, "I don't know who this is and where the photo came from, but it is original" is not uncommon. For 90+% of tintypes, the identity and origin of the tintype has been lost in time.

So, not knowing everything or even lots, about a sign and being able to determine it's vintage and original is not at all incompatible.