Colt 1911 .45 serial # 171885 was manufactured in 1917.
Your colt 1911 was made in 1924.
The government issued Colt with that serial number was manufactured by Colt in 1942.
Your colt 1911 was made for the U S GOVERMENT in 1919.
made by Colt about 1916
made by Colt 1918....................
You must call Colt to find out.
Proofhouse.com has Colt sn data.
Proofhouse.com has Colt sn data
Your colt model 1911 commercial (that is what the C stands for ahead of the serial number) was made by colt in 1917.
Your Colt model of 1911 dates to the year 1918,with the serial number that you have supplied.
1918