Both of the sides that I have were I believe from a double sided sign. They both have the edge that allows for the porcelain side panels and also the front access panel. If it were a single sided it probably would not have the access front panel, you could just reach in from the back. Would really make this sign heavy though putting it back all together with transformers, both porcelain sides, porcelain side panels, and metal angle iron inside framing.
That is why I took the steel frame out and made an aluminum angle iron framework so that it was lighter, worked the same, but allowed for the other side if I had found one.
Now that I did, does that many people really use the double side or do they just hang on the wall.