In my country situation is quite easy. First I ask model what day he was born.
Then (a couple of emails/days later) I ask him for his citizen's N#. This is an 11 digit number (as SSN in USA). It has specific format like: YYMMDD###SV, where YY = year, MM = month, DD = day of birth, ###S = this day birth counter (pair for girls, impair for boys), V = verification digit. The Pesel number (this is how it's called) is unique for 500 years. No two citizens have the same. It is very unlikely to construct a valid Pesel number with correct verification digit if model cheated with his birthday.
And the first thing I check when we finally meet "live" is his ID with Pesel number.