The AT&T clone of the AT pc 6312 has a different connector for its keyboard than
the usual one on most pc's.  The AT&T pc uses a 9 pin DB connector, and most
pc's use a 5 pin din connector.  The signals are the same, though.  So, if
you need or want to, you could make an adaptor cable.  

AT&T pc       common AT keyboard
DB-9            5 pin DIN              function
-------------------------------------------------------
pin 1          pin 2                   Keyboard Data 
    2              1                   keyboard clock
    3,4            4                   ground (return)
    9              5                   +5v
shell          shell                   ground (shield)

Leave the rest of the pins NO Connection.
Before you connect a keyboard to the adaptor cable, check that the +5v
appears on the right pin.   So, you can now use that AT&T AT keyboard
on your AT pc, or use an ordinary AT keyboard on your AT&T 6312 AT pc.
Assuming you selected the correct sexes of connectors for the application!