According to my copy of Clawson's book, the SN should be late 1912 for a Colt. However, the "O" in No. 16442 should be smaller, elevated, and underlined. I agree that the digits are spaced widely, and the font looks off.
The letters in the "UNITED STATES PROPERTY" also look a little widely spaced for Colt. They seem to start in the correct place. Most of the pictures I have of Colt 1911s after SN 83 show the "Y" falling right at the posterior edge of the slide stop notch. However, the Remington-UMC frames look like this one.
The "Model of 1911 U.S.Army" is in block style type, which wasn't used until after SN 178000.
The slide stop appears correct for 1911-1923.
Inspector's mark is from Edmund E. Chapman, who inspected Remington Arms-UMC from Aug 1918 to Jun 1919, SNs 1-21676.
If the SN is original, and I haven't seen enough photos of Remington-UMCs to have an opinion on that, it's a 1919 Remington UMC frame and a post 1917 Colt slide.