Proofhouse.com has Colt sn data.
The ithaca made 1911A1 was produced in 1943.The serial number range was 856,405-916404.there was a total production for the war effort of 60,000 handguns.Your serial number falls within that range of numbers.
Model 1911a1
Your colt 1911a1 was made by colt in 1945.
Serial number
That is not a serial no of a Remington 1911A1 they stopped in 1945 with 2465139.
1945
In 1918
About 1943.
1943 by colt
made about 1917
Made in 1941.
It was manufactured in 1944.