If that tanks been welded on I wanna meet the guy who did it, because he left zero trace of it on the outside... To me it looks like a tank that never went through emblem pocket stamping or a repop made by another company. If it is a modified stock tank that once had emblem pockets they were filled/removed by a master panel beater and their work should preserved for the ages as a masterpiece of custom work. Either way it's very intriguing.Shine a light down the filler at the sides and see if there's any weld seams? If it's clean metal you got a real oddball there.