Inspector's marks on WE phones?

[poplar1]

There has been some discussion about the pencil marks found on WE phones--graphite pencil marks on 302s and grease pencil marks on later sets. On 302s, there are sometimes first names and on later sets just a mark.

Were these marked by inspectors at the time of manufacture, inspectors after they were refurbished, or technicians in the field when they replaced a part?

Here is a phone that Mo is currently selling on Ebay. It appears to be new or at least never refurbished or repaired. Yet it has a blue grease pencil mark.