This gun appears to have a hidden third bite. That translates into a "lump" between the barrels that mates into a slot in the action face and the "lump" is locked down by a sliding bolt. The "hidden" references that the slot and lump are not visible when the gun is closed. "Third bite" refers to the "lump" as "third" after the two bites in the main, underbarrel lump. I don't recall the use of hidden third bites on BL of turn of the century vintage.
Miller single selective triggers usually have a unique three position safety selector (right-up, safe-middle, and left-down). A photo of the trigger and safety selector should clear this up.
The "DL" monogram clearly refers to former ownership by David Letterman - no question on that one (joke).
