I'm no expert on Colt 1917s but I have one. I believe the government issue had 5.5 inch barrels and wooden stocks. At least mine does. Check the bottom of the grip frame. If it's a 1917, it should say "U.S. Army Model 1917" in four lines on the trigger side of the lanyard swivel. On the other side of the swivel should be a number that is not the same as the serial number on the crane.

I also have New Service made in 1906 in .45 Colt. It has a 5.5 inch barrel, but they were made in 4", and the hard rubber grips you describe.

So I suspect you may have a commercial model, not a 1917.

If it is in fact a 1917 that has been altered and the grips replaced, ball part value as a shooter in my area would bd $450-500.

If it is commercial New Service in the condition you describe, $1200-1500.

The 1917 would be chambered in .45 ACP with room for moon clips. I believe the 1917 was the first Colt chambered in .45 ACP. The New Service was available in several different calibers; .38-40, .45 Colt, .38 Special, etc.