KELLER IN DALLAS One The young man, who would have looked owlish even without the round eyeglasses, unfolded a piece of paper and laid it on the counter in front of Keller. “The certificate of expertization for Obock J1,” he said. “Signed by Bloch and Mueller.” He might have been a Red Sox fan invoking Ted Williams, and Keller could understand why. Herbert Bloch and Edwin Mueller were legendary philatelists, and their assertion that this particular stamp was indeed a genuine example of Obock’s first postage due stamp, designated J1 in the Scott catalog, was enough to allay all doubt. Keller examined the stamp, first with his unaided eye, then through the magnifier he took from his breast pocket. There was a photograph of the stamp on the certificate, and he studied that as well, with and without magnification. Bloch and Mueller had sworn to its legitimacy in 1960, so the certificate was old enough to be collectible in and of itself. Still, even experts were sometimes careless, and occasionally mistaken. And now and then someone switched in a ringer for an expertized stamp. So Keller reached for another tool, this one in the inside pocket of his jacket. It was a flat metal oblong, designed to enable the user to compute the number of perforations per inch on the top or side of a stamp. Obock J1 was imperforate, which rendered the