It comes as a complete surprise to me to learn that in standard English there is no such word - or contraction - as amn't. The proper contraction, so I learn, is aren't.
I'm here, amn't I? - Not Standard English
I'm here, aren't I? - Standard English
Well, this is a surprise. In Scotland, amn't is used in normal speech, without any connotations of it being slang, or improper English. I've used the word all my life and didn't even realise it wasn't normal. Although I have been in England for 30 years or so. Obviously I never noticed I was the only one using it.
Possibly this is something everyone else learned at school, while I missed out. Hmm. It may have been the day I bunked off to get Led Zeppelin tickets. Or maybe some day I just failed to turn up. I didn't have a great record in my final years at school.