These are some service marks on a gun I own---and that I sent back for work. I do not actually KNOW what these marks mean (some of them anyway), but I know what I asked them to do----and I know what they did---sort of.
The date stamp is easy: 460---April 1960----LH grip frame (where the "stocks" go).
S<> on the same grip frame.
S <> on the barrel flat.
S <> on the cylinder (under the ejector).
What did I ask for? Refinish from matte blue to bright blue----because I wasn't willing to wait six months for a special ordered bright blue gun. It took two weeks this way. I asked that their very best craftsman go through the gun and make it as perfect as it could be.
What did they do? They refinished as instructed----with absolutely NO sign it had been refinished. They changed the timing of the bolt/cylinder stop such that there's no turn ring (except for about 1/16" just before the lead into the cylinder stop notch at each chamber-----after fifty some odd years, and about a half a boxcar full of ammo run through it. Whatever else they did was magic, because it was/is SLICK!!
What didn't they do? They didn't do anything (besides refinish) to the barrel. So why does the barrel carry the service mark noted above? Good question. I have no answer. Ditto for the cylinder.
That's it---end of report.
As an aside (on another gun). This is a nickel gun from the 30's---very spiffy. Star on the left side of the grip frame. Star on the cylinder (under the ejector). Star on the barrel (inside the ejector rod shroud). Star on the yoke/crane. Star on the inside of the sideplate. The innards appear to be brand new. This gun was shipped to a police department. It was either put into a sock drawer immediately upon arrival---or was COMPLETETLY rebuilt later on. When? Another good question. There's a five digit stamping on the left grip frame---no .'s, no -'s, no /'s, no spaces. Could it be a date? Absolutely---one of two different dates actually. There are no other markings of any sort (other than typical fitter/inspector codes).
Go figure!
Ralph Tremaine