Very interesting mailbag.
I suspect the PCB may have been made by IBM. It looks similar to some boards that also had DTL in them in that era. IBM created the computer used in Apollo 11, so maybe the one in the mailbag an IBM developed board. That same Apollo 11 computer technology was used in the IBM Series/1, a system I really enjoyed working on in the early 1980's.
The Series/1 was an incredibly flexible machine employing open ended architecture. The applications were extremely varied - overnight money market communications interface at the major banks, Telecom directory assistance, hotel management, and processing for the oil industry to name a few.
The smelliest application was a big laundry company in Melbourne that washed hospital bed linen. The Series/1 was used to count dirty bedsheets as that were thrown down a shute. I have to literally run holding my breath to get the the machine to work on it, especially in the summer.
![Phew :phew:](https://www.eevblog.com/forum/Smileys/default/phew.gif)
The strangest (and second smelliest) application was at the Howard Florey Institute at Melbourne University. The Series/1 was connected up to a number of sheep to measure hypertension via the salt content in their flesh.