The VOIDRUNNER'S CODEX is coming! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
Late reply, but I didn't see any other comments that said what I thought about it.
The coin is probably symbolic of the toll Durnan charges when someone wants to go to Undermountain. 1 gold to lower someone down, and then 1 additional gold collected in a lowered bucket before he lets you come back up.