By accident I heard activity on 10 meters this afternoon, and it sounded like a contest, and it was open to the US, east coast.
So I hurried to call, got a few contacts, scribled down on some random paper. I just sent my 599001, 599002, and a few more. Until I heard someone from Europe send 599500 twice.
Oh, yes, the ARRL-contest, where you had to send the power, not a serial number.
But for most of my 10 contacts I got it right. Always be positive!