Internal 845 tube glass markings

What are you thoughts on these internal brown markings? This is an early 60's RCA 845 purchased from a very reputable and well known tube dealer, here in the US. It was sold to a friend as pulled and used, but testing as new, > 90 and 100% emmisions. Another friend of mine who builds tube amps thought it might be indicative of prior arcing, but this tube works well and is quiet in my friends Cary 211 FE. He put maybe 100hr's on it along with 3 others from the same dealer that do not show the same internal brown markings.

Hmmm??