Assuming you don't mean traditional as in "counts as traditional for the Traditionals subforum here," Spyderco makes excellent lockbacks in a wide range of steels. VG-10 is good stuff, H1 is rust-proof, S30V and even more exotic stuff can be had (K390, etc.).
Although not technically a traditional lockback, because the Tri-Ad lock functions a bit differently, the Cold Steel AD-10 is fantastic and operates exactly like any other lockback -- and, based on your request, might be one of the best CS knives to choose. It has the smoothest, easiest to disengage lock of any CS knife I've owned. Second easiest is probably my 4-Max Scout, but that knife is a monster rather than a more general-purpose tool.