Beautiful and interesting frame; this is the EM Pro SLX (model later renamed Corsa Extra) from autumn 1985, one of the initial Panasonic "camo" (two track frames for Panasonic cyclists - Hans Lubberding and Bert Oosterbosch - for the 1986 season were marked Z4586 and Z4590; your frame was built the next day - probably Additional chroming of the frame elements was an option (similar to the brake cable inside the top tube ... and number hanger btw). The "narrow" geometry of the rear triangle (without seatstay caps) and v.1 Silva brake bridge with v.2 inscription Eddy Merckx - everything fits together perfectly.