What excuse can I give to look at my boyfriend's driver's license without sneaking into his wallet?

I think he's lying about his age. He said he's born in a certain year one time, but mentioned his numerical age differently another so I want to be sure, it's bothering me a lot even though it's a year difference. (he told me he was born in 1973 a couple of times but in person told me he's 36...his birthday is in a few months..there's no way he could be 36 if he was born in 73). I don't want to tell him I don't believe his age and stir things up.