I have no idea just looked up Master in dictionary � A name for a boy who is not yet old enough to be called Mr. No help whatsoever. But I said 16 and my mate said surely 18 as this is when you become a man and can drink and vote. Like drinking makes you a man :-) But I said when 17 you can drive and Mr is put on driving license. So I stick with 16.
My 13 year old son has Mr on his bank cards and I'd think 13 myself as it seems too old to be called master ( is that even used much anymore?I've not heard it in functioning use for ages). I think it's one of those subjective things where you can't be right and can't be wrong, so whatever you think.
Master is an old British term which usually means a boy under 13 in formal correspondance. In evelope ettiquette he is Master until he reaches 8 years old then he is just address by name then at 18 by Mister
This is an awkward one, in my day, you had to start paying full fare at fourteen, so technically, you were an adult, but you were still at school, weren't allowed to vote or go to work etc, but i'd say the voting age, because your allowed a say in who runs the country.
Surely men should be adressed as 'Master' until they get married, much like 'Miss'. I think that would be highly appropriate. Then men would have to come up with a feminist equivalent of Ms.. Maybe Mazter....?