Essex Arms manufactured frames and slides that were sold by Brownells, Midway and other firearm parts suppliers. They are currently setting up a new plant according to their website and have not produced any frames since 2010 or earlier. The web site still says they will be up and running in mid 2011 and directs you to the Iver Johnson site for 1911's. They are selling for $581 to $824 depending on the model and upgrades.
I have used the Essex frames to build quite a few guns and they are excellent to work with. Most parts fit without a lot of extra work, just normal fitting.
The 1917 Enfields were produced at Remington, Winchester and at the Eddystone plant in PA that was run by Remington. It is a 30.06 with a 26" barrel and 5 round integral magazine. The original finish was a high polish blue, but wartime produced guns and reworks can be matte black or parkerized. Reworks are guns sent back to an armory to be repaired or rebuilt. Parts can be from all 3 manufacturers and numbers may not match. Values are:
High Polished Blue Matte, Parkerized or reworked
I hope this helps you,
Sorry, I got stuck on another question.
The serial number doesn't make any difference. It is the frame only and not a complete gun made by Essex. They will make frames for you with custom numbers if you request them. I can have a number like THT308 put on a frame by the manufacture when I'm building a custom gun. As long as the number wasn't used already on that series or model frame.