Joist braces were made to work in tight spaces where a full brace and bit wouldn't fit.
Various models were made, a common version was the Skinner joist brace.
This model has no identifying marks
1) Modern features, ratcheting mechanism.
Early features, bit holder, screw out back support.
2) Note: screw out back support
3) Early bit holder
4) back support wound out.
5) back support wound in
6) Bit holder and thumb screw. Ratchet mechanism
7) Ratchet mechanism and back support.
8) Handle