about 1917
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.
I thought that would be in the end of the serial range of Ithaca but 1944.
Model 1911a1
Ithaca made 382,000 of these between 1942 and 1945, but I don't know of a source for narrowing it down farther than that. Not sure about the serial number, as Ithaca was assigned serial numbers of 7 digits, beginning with 1,208,674 and ending with 2,693,613, but not sequential. Ithaca was awarded the only "E" for excellence in manufacture of these pistols of the 3 companies that made them for the military.
Look in "The Ithaca Gun Company - From the Beginning"
Ithaca and Remington Rand didn't manufacture or ship wartime 1911's in numerical order. I'm afraid the best estimate you'll get is that it was made about 1945 as part of the effort to supply soldiers in WWII.
Your colt 1911a1 was made by colt in 1945.
1916-fluse model
Serial number
That is not a serial no of a Remington 1911A1 they stopped in 1945 with 2465139.
about 1945
made about 1943 by ITHACA firearms company