I recently acquired 210B Adjustments and 1143B Parts manuals for the Sequential Selector (BS2. BS3. BS6). Let me know if I need to move them to the top of the "to be scanned" pile.
I added some photos and a short description at
https://www.navy-radio.com/tty/seq-sel.htm

Cheers,
Nick England K4NYW
www.navy-radio.com