• Both S&W (top) and Colt (bottom) variations differed both in physical appearance and functionality. 
  
  
  

• The S&W variant (top) could fire .45ACP cartridges without the use of half moon clips, however, each case had to be manually removed from the cylinder after firing. The Colt's cylinder was manufactured such that it required  half moon clips to fire.
  

• Brad Pitt's character in "Fury" used a S&W M1917 revolver as his personal sidearm.  His revolver sported a set of plexiglass "sweetheart" grips in place of the USGI walnut set normally issued.
  

After the outbreak of WWI it became readily apparent that the United States military was not equipped with the number of Colt M1911 pistols it needed. 

The military's interim solution was to ask the two major American producers of revolvers to adapt their heavy-frame civilian revolvers to the standard .45 ACP pistol cartridge.

Both companies' revolvers utilized half-moon clips to extract the rimless .45 ACP cartridges. Smith & Wesson invented and patented the half-moon clip, but at the request of the Army allowed Colt to also use the design free of charge in their own version of the M1917 revolver.

Over 300,000 M1917 revolvers were issued to frontline troops in WWI.  During WWII the pistol was issued to specialty troops such as tankers and artillery personnel.  During the Korean War the pistol was issued in small numbers to secondary and non-deployed troops.  The M1917 made a resurgence during Vietnam as a very capable, reliable, sidearm for "tunnel rats" performing underground search and destroy missions in the Viet Cong's vast network of tunnels.