You will have to call Colt to find out.
Colt 1911 .45 serial # 171885 was manufactured in 1917.
A Colt government model .45 with that serial number was made in 1917.
The age and value of a colt .45 peacemaker serial 180356 are about 1900
Colt army .45 with that serial number was made in 1944 by Remington Rand for Colt.
I think the Colt cowboy .45 came out after 1998.
1164728
That Colt was made in 1891. Colt started with serial number144000 in 1992.
The Colt government 1911 .45 with that serial number was made in 1944 by Remington Rand
A Colt semi-automatic .45 government issue with that serial number was made in 1919.
Colt or S&W
You will have to call Colt
Proofhouse.com has Colt serial number information you can use.