This item has a slight blemish on the mortise lock faceplate and is priced accordingly.
NOTE: Sold as is. No refunds, returns or exchanges on blemished items.

Atrium Door Hardware, Lever Style Brass Mortise Lock.
The Atrium lock hardware -set includes everything necessary for replacement, including screws and strike plate.

Levers: 4 -1/2 Inch Solid Brass Mortise Lock
Backset: 1-3/4 inch (45mm) narrow stile
Door thickness: 1-3/4 inch
Lock faceplate measures: 15/16 by 9-5/8 inches.
Handle Escutcheon Plate: 1-3/16 x 8-1/4 Flat, 3 screw holes, solid brass
Cylinder Type: Single cylinder lock, Crescent thumb turn inside.
Atrium Keyed Cylinder: rekeyable Schlage SC-1 keyway with 2 keys
Spindle for handle: 5/16 (8mm) x 3-1/4 inch (83mm) on the Square.
Distance from the center of handles to center of Cylinder 3-5/8 inches (92mm)
Handing: This handle set can be used in Left and Right hand applications.

Color Options:
Polished Brass
Polished Chrome
Satin Nickel

For help with installation of Atrium locks, please read The Atrium Lock Installation Instructions. 

NOTE:
To change to the 40024 (keyed) or 40031 (non-keyed) trim hardware you will have to drill a new hole about 5/8" above the existing top screw hole. The trim plate is longer towards the top and will cover the existing top screw hole.

The bottom portion of the plate is slightly smaller (~1/8 inch), and will leave a small part of the old trim imprints visible.

Priced and sold each.

Resources:
General Information on Atrium Doors: Guide to Atrium Doors
Guide to Installing Atrium Locks: How to Install an Atrium Lock