1992. A single dash was the date code for 1992 but there was an engineering change early in the year so a second dash was added to differentiate. That made the double dash more common than the single dash. The following was posted by Joe Houser in 2007.
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110 Folding hunter 1992 double dash
In 1992 the date code on our blade stamps was a dash, just after the model number. BUCK, 110-, U.S.A.
As many of our loyal forum members know, later in 1992 a second dash was added to the 110. BUCK, -110-, U.S.A.
Our engineering group gave me the explanation as to why the second dash was added. Apparantly, there was a design change in the blade radius area that warranted the stamp code change.
The goal of this design change was two fold. Make the action smoother, and eliminate an opertation in the shop. It was not a very noticeable change to the naked eye. I compared a 1994 110 blade to a 4 dot i just happened to have on my desk and any diferences were hard to see but they are there.
So there you have it, mystery solved!
Joe Houser
Director of Consumer relations Buck Knives Inc.
Buck Collectors club Liaison, Member #123