I'm far from an expert but here's a copy and paste from the FAQ dealing with damascus:
Left to right: 'D4' - Quality 4 Damascus, 'C' - likely barrel maker or finisher,
'4, 1' - pre-finish barrel weight, '3' - Grade 3 or D, '2' on the lug - frame size. Courtesy of Greg Baehman
https://lh6.googleusercontent.com/-Q...rrbtXtNdQQLqOv
GH courtesy of Dave Miles