I understand the issue that you have raised, but I think the issue may be that different people will have a different requirement of proof before attribution becomes fact.

As an example (only because it is one that applies to me personally), I have a fractional chip that I got from my local casino in the UK. It is a 50p fractional that I got at the bkackjack table. Same suits mold, same brown colour, same hotstamped denomination BUT no casino name. I can only assume that it shouldn't have been put into play but was either missed or, because the casino (the old Westcliff if anyone is interested) always had a shortage, perhaps they didn't have a choice - and after all, no-one was going to bother to fake 50p chips

So, the point is, I know I got it from the Westcliff and list it as such in my collection. But other than my word, there is no proof. It is a generic chip so I suspect that even if manfacturer records were available they wouldn't tell much.

So does this count as an attribution or proof? To me proof, possibly to others an attribution. To people who don't know me, maybe not even that

My point is though, I believe that the information is useful as I know that the chip was in use at that casino, and (IMO) it would be a shame if similar information was not made available to others just because it couldn't be proven.

Just my humble opinion - each to his own!

Jason