Andersen dummy cylinder housing in Brushed Chrome.
Brushed Chrome lock set dummy cylinder fits all trim set styles except Tribeca.
Installed with 2 mounting bolts
Removed when installing a keyed cylinder

Priced and sold each.
2579499 - Keyed Cylinder, Bright Brass
2579540 - Limit Plate
2579542 - Lock Actuator
2579824 - mounting bolt

 
How to Replace a Dummy Cylinder in an Andersen Handle Set with a Keyed Cylinder