My mate worked at a photo development lab and said if any photo's were dodgy they were supposed to destroy the photo and negative. What they did though was have a "glory wall" in the Lab where they would pin them all up 😆
I discovered recently a bag of wallets of old photos. I'd say half were out of focus, not to mention not having a clue who half the people were in them. :lol:
Mine used Eucryl and I remember as a teenager trying it once. It took all the stains off my teeth. In fact I think it took the top layer of enamel off too. Never tried it since. PS never been a smoker.