A stepping motor BOSS machine cannot DNC. It needs a separate DNC loader that bridgeport built. In 30 years of field service, I have seen only one.
There are devices that are called BTR (behind tape reader) but I have no experiece with that either.
Bridgeport sold the same smart box you have and called it a EZFILE. Back then they got about 5 grand for it. (mid 1980s).
It does work with the BOSS 8 and 9 and above.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)