This is the passive (PS3) lock designed for use in a double door system with no astragal between panels.
This is the center section of the Sentinel Swing Multipoint XP25 2 point passive lock with shootbolts.
The Passive gear box does NOT have a slot for a tailpiece, just a round hole.
The Passive side of the door handle trim does NOT have a thumbturn.
When the deadbolt from active door goes into the receptacle on passive lock, it prevents the handles from moving.
PLEASE review all images, as there are 3 of these that appear to be the same.

Faceplate Length: 40-15/16 inch (1039.6mm) 40.93 inches
Faceplate Width: 25/32 (20mm) inches
by Ashland W5100STPAS3

This part of the multipoint lock is the Receiver gear box with receptacles for the deadbolt and spring latch.
This is 1 of 3 pieces to complete a Passive lock with shootbolts.
Jeldwen, Caradco 4101341
Lower Shootbolt, 36" HH
Jeldwen has Upper Extensions for their doors 77", 80", 93"