1/SSC/338
A special locking screw used on Bakelite Bellset covers when fitted
to a telephone. Threaded end is 2BA. A
Ring-driver No. 5
is used to release and fit the screw head. Pictured to the
right.
2/SSC/338
A locking screw first used on the Unit, Teleprinter, Broadcast No.
3. Threaded end is 4BA.