GGS on left side of M1865 Barrel

[smd189]

Any info on what this means?  Thanks.

[Two Flints]

SMD189,

Maybe the letters refer to:

GGS  =  G.G. Saunders (Colt Dragoon Revolvers 1856) US Inspectors Initials

Two Flints

[smd189]

Thanks.  Are these letters not typically found on the side of 1865 barrels? 

[Two Flints]

Small arms of the United States Army and Navy bear an initial or initials which are called inspector's marks. These marks appear on stocks, grips or metal parts. Some arms, especially older ones, have more than one inspector's initial or initials.
The barrel was inspected before the rest of the arm was produced and thus there may be one inspector's mark on the barrel and another on the rest of the parts.

[Trailrider]

How are these initials applied?  Are they stampings that are regular and appear to be of the same age as the gun?  How tall are the letters?