The only M1917 Commercial in .45 ACP was this one (from Coltfever):
The New Service Commercial Model 1917
These guns had checkered walnut grips with silver medallions, and with the barrel marked "Colt Model 1917 Auto Ctge".
There were about 1,000 made during 1932.
These had 5 1/2" barrels and were in .45ACP.
The last patent date on the barrels was October 5, 1926
There were also some target model New Service revolvers made in .45 ACP:
New Service Target
This was a target version of the New Service, available from 1900 to 1940.It had a flat top frame and adjustable front and rear target sights.
It was available with a 6" (rare) or 7 1/2" barrel.
It was made in bright blue or (rare) bright nickel.
A round butt version was available after 1930.
Grips were black hard rubber until 1913 and checkered walnut with silver medallions after that.
The trigger and back strap were checkered.
Calibers offered were .44 Special, .44 Russian, .45 Long Colt, and .45ACP.
New Service Shooting Master
The Shooting Master was a high grade Target version of the New Service. It was fitted with a flat top frame, adjustable target front and rear sights, a checkered trigger, and back strap.
It was available with a rounded butt or a square butt after 1933.
Barrel length was 6" and the grips were checkered walnut with silver medallions.
Calibers available were .38 Special, .357 Magnum, .44 Special, .45 Colt, and .45ACP.
It was made from 1932 to about 1940.
I have a feeling yours was a M1917 military model probably shipped after WWI. These shipments of miltary M1917s from Colt continued into the very low 3xxxxx SN range. And it has a chopped barrel. Colt's SN data base says that SN dates to 1920. Might be an OK buy if you can get it cheap.