I have been following this thread but cant remember anybody talking about this but helmets will be looked at through a magnifying glass. Rusty buckles and sus chips or if it looks like it has had a hard impact and you will fail. They have cracked down in the moderns and it has started in vintage as well.
This offends me.
This is how car scrutiny happens, and it is an absolute crock - people get told to buy a new helmet because there's a minor chip in the gel-coat, or whatever.
I currently own four helmets:
1. Took a solid thump when I fell off my MTB many years ago.
2. Has had little use and have never been 'used', but has a few nicks in the graphics and fails car scrutiny.
3. Took a solid thump when I broke my leg at Buladelah last year.
4. Is my 'good' one, bought to replace #3.
The thing is that both of the two damaged ones look fine (if you ignore the broken peak on #3), and #1 sailed through 4 or so years of car event scrutiny.
Personally, I'm a LOT happier with the idea of #2 on my head, but this illogical idea that cosmetics somehow relate to safety means that I can use it. The same illogical rule encourages me to use either of the helmets that have already done their job, and have much, much to offer in any future crashes.
Similarly, a bit of surface rust on a cheaply chromed buckle has no relevance to the helmet's performance when it matters.
If you took a helmet with a buckle that was rusted halfway through and a strap that was cut halfway through, and then tested the strength of the strap assembly, you'd find that the wearer would be in a world of trouble well before either helmet component failed....
MA has/had been doing it right - check for standards approval, check for obvious, significant and relevant defects. And never forget that the person wearing the helmet has the best knowledge of the helmet and has the most to lose if they make an overly gung-ho decision...