They buy, sell and service older collector cars. Two years ago I drove by when the door was open and I saw what
looked like a 1938 four door Packard Convertible inside.
Whiplash..hit the brakes. 
The car was Not a Packard, but a four door Dusenberg Convertible with a second windshield protecting the rear seat. I talked to a very knowledable young guy working on the car. I looked it up when I got home. It was worth over $1M. I think it was Green.
The year before, there was a 1940-41 Lincoln Zephyr V12 Convertible for sale. I think the price was $40K.
I keep my eyes peeled every time I go by there. You never know what you might see. BTW: I think they are TWO seperate busineses.

NB
http://en.wikipedia.org/wiki/Duesenberg
EDIT: I believe the "Model J" referred to the chassis and running gear. The "SJ" probably stands for supercharged. Every body was different.