Old Aircraft NC registration records

Off topic perhaps, but does anyone know where archival US aircraft registration records are kept?
Specifically, I am trying to find out who owned NC655K, Cessna DC-6A c/n 225 around 1934/35.

I didn’t know Cessna made a DC-6! Here’s a picture:

My suggestion is to contact the San Diego Air and Space Museum. This is the organization that supplied the picture above.