Howard Hughes Spy Ship Sign

I recently purchased a cabin in California, in the basement of the cabin, which was built by RCA Victor Company in 1932, was a very long wooden sign which was wrapped in blankets. It still has the original masking tape on the front which is to protect the wood finish. the sign appears to be new/never used.
The sign says "HUGHES GLOMAR EXPLORER" which turns out to be a spy ship commissioned by the CIA and built by Howard Hughes. The public was told the ship was a oil rig, but it was really built to raise a sunken Soviet submarine.
I'm trying to find out anything I can about the sign.