David,
The serial number for the pistol is found on the frame where cylinder crane closes against it.
The same number is also on the crane as well. Serial range as James noted, most likely in the 629,000 to 652,000 area.
The number on the butt is some sort of ID number for the gun. Combined with the lanyard, my guess is that it was lend-lease.
The 38-200 OPs do command more money than the .38 Specials when found in collectible condition. Most of them in that caliber ended up in England during the war.
The marking on the left frame at the junction of the trigger guard and frame is Colt's 'VP' or verified proof.
If the gun is British marked, you would see it with stampings that are hard to miss.
150 or less - 650 or more without pictures. Take your pick. If the guns finish is in the high 90s it would sell quickly.
JT