1930 Sport coupe with hydraulic brakes

[Seattledavid]

I have a 1930 sport coupe with hydraulic brakes and I believe it has a 1939 backing plate. There is a gasket on the rear hub that I have not been able to find from any of the vendors so don’t know if it is necessary. The first photo I attached shows it in its normal position and the second photo I moved it up so you can see it better. Does anyone know if they are available or if they are needed??

Dave