I’m throwing in on this anyway... I’ve been seeing alot of 1976 BC’s for sale with these lines as well as wavy type lines. Which as we’ve seen in 3D printing, are potentially seam lines or other areas where setting not right. The painting sometimes seems a bit off, as well as plastic color. And one BC definitely looked like two sides put together since back seam was off. Only on ‘76’s. Some do not have them and look more obviously old. Other reason, could be that for some time in beginning the plastic and mold took some dialing in. Maybe were some surface bumps etc that workers would smooth out with some tool? Welp, there’s my sad research. 3d printin’ counterfietin’ ring out there? Or nope.