I think that the tape or painted lines are used for identification for shipping. I once owned a Purdey that
had black lines on it and on the top of the case under his name it was stamped "The Rifle Brigade". I now have another oak and leather case that has the same black lines on it and also a big black X on the cover centered on the center medallion. My guess is that when a military unit was being
redeployed they had the lines on the cases to make them
easier to identify. Just a guess.