a stunner and agree that high quality photos really do it justice. No idea of make or nationality but a saddle with "Berlin" stamped on a saddle rivet seems a very strong clue! And the subtle "points" on the stay ends seems to be a touch favored in places like Austria.I think the "J S" and cap "A" are transfers like you might find for hobby or even ceramic use, must have had some meaning for the (earlier) owner. 27 seatpost means that if Columbus tubing this is SP, as expected for track, or at any rate a heavier wall tube for seat tube.