mr.e moose:
You have a British Service Revolver manufactured between May 1940 & April 1941 when the Lend Lease agreement between Britain & the USA took effect, with guns receiving US Property markings.
Prior to World War II Britain's standard service cartridge was the .38/200, a .380 Revolver round with a 200 grain bullet. The .380 revolver round is the same as the .38 S&W. In 1940 the British & Commonwealth governments ordered a variant of the .38 Miltary & Police Model of 1905 4th Change chambered in .38 S&W instead of the usual .38 Special. This is the British Service Revolver.
S&W delivered these with .38 S&W CTG stamped on the barrel. The owners stamped them with their own markings, and at least with the British revolvers, when sold out of service they were stamped with British proof marks, including .38/.380 marks.
60736 is an assembly number, used to track parts in the factory. It has no meaning after the gun is assembled and is not recorded by the factory.
821064 is the serial number, it was not uncommon for S&W to stamp this on the barrel and cylinder in addition to the bottom of the grip, it should never have been ground off the grip as it must appear on the frame. I would contact a local gunsmith about getting the number restored on the butt, you may have to get the ATF to ok this. Consider the hassles involved a small price to pay for avoiding the possibility of some small minded official in the future deciding to bust you for having a defaced pistol.
The patent numbers are correct for the design changes brought in by S&W in 1915, including a non positive hammer block safety. The current positive hammer block safety was developed in 1944 after a fatality with a dropped gun. If you keep this gun loaded it would be prudent to leave the chamber under the hammer empty.
A lanyard ring and smooth walnut grips were standard for these guns, Numrich arms should be able to supply you with a second hand lanyard ring if you want one.
A lot of British Service Revolvers were converted to .38 special after the war by boring out the cylinder. The rim end of the .38 S&W case is wider than the .38 Special case, so the .38 special is a loose fit and bulged or split brass can occur. Check if your gun chambers a .38 special. If it does then only shoot standard velocity lead loads through it, no PlusP.