Re: New Service 455 ELEY
That gun is a Colt New Service. It was made in 1914, in .455 Webley (which Colt called the .455 Eley), one of tens of thousands delivered to Britain prior to U.S. entry into WWI. More thousands were purchased privately by British and Canadian officers. Many were stamped with an "E" (England? Eley?) under the left grip.
Serial numbers of the .455 caliber were not contiguous, but are in the range from about 65000 in 1914, to about 139000 in 1917, when production was dropped in favor of the U.S. Model 1917, a modified New Service chambered for the .45 ACP.
As to value, my first impression is that the pictured gun has been reblued. If it has not, and is in that condition, value would run around $1700; reblued, the value would drop to about $600. Values given are retail prices.