If the legal carry length is 2" (is that it in PA?) and a cop doesn't want to mess with you, he'll measure from tip to back end of "edge" (if he even cares to measure at all). If a prosecutor wants to try you, he'll measure from tip to handle, even if the edge stops 1/4" from the handle.

Most knife manufacturers measure "edge" length when quoting specs for a knife. You may get it and realize the exposed steel is (sometimes substantially) longer than what the specs said. In a legal battle, you would certainly use that as a defense.