Lucy's casket was built solid, weighing approximately 45 lbs including lid. The coffin featured a deep bottom for the actress to hide in when casket was set at the right elevation.
Count Dracula's casket used the same lid as Lucy's, sans the cross detail. This was only a half-coffin that was securred to the bottom of the bed on the set. For the last scene of the show, the bed transformed into a wagon that carried the coffin to Castle Dracula.
Also seen above, the French doors behind the bed transformed into the portcullis at the front of Castle Dracula.