The master key opens all locks, the valet key opens everything except the trunk. (I believe you twist the master key the reverse way of 'open' and it locks the trunk to the valet key...and you can lock the seatbacks from the trunk to prevent them from opening, so this isn't as stupid as you'd initially think.)
Thank you for your replies. It seems that either the trunk doesn't have the original lock, the trunk lock is broken or I was given two subkeys. Neither of the keys that I was given will even fit into the lock. Both keys will only fit a small way into the lock before stopping.
sounds like the lock is busted to me, or there's a broken key inside it; even if it wasn't the right lock it would still go all the way in, it just wouldn't turn. Locks rust inside and get seized up so it could be that also.