Colt Service Model Ace Serial Number SM355 - Early variation with earliest style slide markings.  Pistol was shipped to the U.S. Government, Springfield Armory, July 26, 1937 in a 155 gun shipment. 

Left side of slide has patent dates that appear on the Model of 1911 and Government Model pistols: 

Right side slide markings are from the Ace roll die with the words "SERVICE" and "MODEL" on opposing sided of the bottom of the Ace diamond on the right side:

Pistol SM355 has matching numbered slide. This pistol was in an early shipment on July 20, 1937 to Springfield Armory.  Additionally, there is a record in the Springfield Research Service of SM355 indicating the U.S. Navy received it from Springfield Armory on November 2, 1937. 

Colt Service Model Ace Serial Number SM355 - Right side

Colt Service Model Ace Serial Number SM355 - top of slide showing earliest style Stevens rear sight, floating chamber and front sight.

Colt Service Model Ace Serial Number SM355 - underside of frame, front grip strap, non-lanyard loop mainspring housing and earliest style Ace marked magazine base plate.

Colt Service Model Ace Serial Number SM355 - top view of Stevens sight.

Colt Service Model Ace Serial Number SM355 - rear view of early Stevens sight.  Note the use of fire blued screws on this early sight.

Colt Service Model Ace Serial Number SM355 - ejection port showing floating chamber and early style slide markings.

Colt Service Model Ace Serial Number SM355 - Earliest style Service Model Ace magazine.