Yes, the "W", the inclusion of the practice, and no "BS" markings are govt-issue indicators. (You know, of course, that the "M" in the string stands for modular.)
They plugged into 75-pair or 125-pair (in the case of 30-button CD's) cables, e/w (equipped with) either 3 or 5 female connectors, installed at the factory. Or in the event that the customer needed an upgrade to an 18-button CD, from a 6-button phone, the installer might run two more 25-pairs, or a 50-pair cable.
You might consider attending the TCI Lancaster PA telephone show that occurs this year on June 7th and 8th. Lots of neat old phone stuff, and a "Switcher's Corner" where members who are operators of nodes on C*NET assemble working PBX's for demonstrating the private network to which many of us are connected.
See
www.CKTS.info for example.
