Crimea_River
Marshal
The seam, if it was present, would be very subtle in my opinion since the upper cowl was intended to be entirely a one piece unit, albeit made up of many components. The seam might be where two fixed sections of stamped aluminum sheets butt together. Maybe they initially stamped two mirror-imaged pieces and later found a way to stamp the entire section, I don't know. Interesting detail but, if it were me, I wouldn't bother with it frankly.