Jay,
That is a "Singing Chapel on Wheels". It is a 78 RPM record player that you can play music on at the Graveside. There is a loudspeaker under the hood. They were available during that era (1939-1942) for any coach. I have not seen another one, but they were advertised in the industry. This car did not have one when I bought it, but I found this one in Texas in 1974. Lo and behold, I got ready to install it and there were holes already drilled in the right places so it was a breeze to install. Obviously this car originally had one............
P.S. Had a place to plug in microphone too. The case has an angled right side to clear kick panel, and bolts to firewall and dashboard.