Here's another assumption....
I've been in the petroleum equipment industrie for 30+ years..
In the early 80's, I worked for a contractor that serviced the Major Oil Companies such as Shell and Imperial Oil..
Repairing and rebuilding air meters was part of our service.
I dont know if the oil companies purchased their meters directly from the manufacturer or not, but it would make sense that they did (according to Jack's assumptions)because mostly all of them had to be taken apart to change the glass and re-install the chrome pieces from the inside.
On the other hand when we serviced Independants, many of the chrome pieces were installed with the screws on the outside, which leads me to believe that these meters were purchased from a rebuilder such as PMP.
These are just assumptions, but from my experience, Jack's theories are correct.
