Detail I keep coming back to.
A daemon's horns come in heavy and low, the way a ram's do, and they are ribbed the whole way. Each ridge is a season of the trade, laid down like the ring of a tree. They grow in slowly over the first years, curling further with each soul brokered and each contract kept.
So an old daemon's crown is a full accounting that a stranger can read at a glance. This one has been dealing a long time, and dealing well.
The bit that makes it work: anyone who has kept sheep can count them, and on the verge a good many people have. Your professional history is written on your head in a notation every farmer already knows.
People also watch for filed-down horns. A daemon ashamed of their crown is either the most dangerous kind to deal with or the only kind worth trusting, and nobody agrees which.