Yes, it's about the same size as a standard marquee. It's a little shorter than most, though. I'll get the dimensions tonight and post them here.
Data is persistent across power cycles, but apparently not if you leave the sign off for a very long time (I believe it's about 1-2 months). I'm guessing that the storage on the sign isn't totally nvram-like. It has a single power source, (do you want the voltage?), and has a rj45-serial cable for a PC connection.
Just to let you know, the reason I'm selling it is because it can't be programmed on the fly without custom software and some reverse-engineering of the sign's control protocol that goes over the serial line. But, if you have the time for it, it's not impossible.