CCKW Mystery Bracket

[jim sewell]

1942 CCKW A1 bracket.
Could I have some help identifying this bracket fitted to the tray of this GMC .
It has a plate bolted to the floor with a couple of slots in it .
It has the remains of a retaining strap at the top of the board .
There are two retainers that can be tensioned with large brass wingnuts

Thanks
Regards
Jim S.