1304 Bearded Washington Flaw?

This coil strip has two stamps with a vertical line down his forehead. Is this a constant variety or what?

A typical true plate variety on a coil of this era would occur every 48 stamps. I will vote for "or what", specifically ...

I think this is a mark left by a vending machine. Insert a quarter for 5 stamps and pull the handle or turn the crank. It advances 5 stamps and some internal device clamps down on the strip. Over time the pressure of the dispensing device slightly abrades the coil and picks up ink and redeposits some of it every 5 stamps. Note the line is slightly different on the two end stamps. The buyer bought several transactions worth and later saved a strip to retain both machine marks straddling the joint line. Without seeing your strip in-person, that's my theory.

John - Thanks! That makes perfect sense to me. It is an artifact, not a plate flaw, which certainly would have been reported long ago, if not detected before production.

may be mark from coil dispensing machine

for some reason I did not see John's response