National Lumber Company Nails are very diverse. From 1924 to 1933 they are Copper Indent.The Steel Dates go from 1934 to 1939. The 1934 Steel comes in 2 varieties. They are both indent, but one has "NLC" on it, and the other has only the "NL". The Steel Dates 1935, 36, 37,38 also have both Indent and Raised Dates. Shank lengths also vary on several dates.