Dorgath determines that it is not a special lock. It seems to be quite old, but it's just a regular lock. Hypothetically, it could probably be opened with some dwarven lock tools, such as the ones that Dorgath is carrying.
[Yeah, for a while I had Skullcrusher figured as being more of the thief-type character for the group, but BB up and disappeared before the ball ever got rolling on this again.]