I'm guessing you don't know what the original glue was. If its not stiff, its likely contact or barge cement. If its crunchy or stiff, likely wood glue. Either way, if its not peeling off the leather, sand it down a little and it should be good to go. If its not in good shape, sand it way down, or you should be able to soften it with denatured alcohol or acetone. I would not soak it with solvent, just lightly scrub it with a dampened rag or scotch pad.