When I first heard about this piece, I thought it was surely a wood pattern for the Hall of Justice. A few minutes later I learned it was a tad different. A few minutes after that I bought it :^) This piece was created by a pattern maker and was most likely used to create a mold for casting vaccu-form sample playsets. This is why I use the term wood model as opposed to wood pattern. It is carved from cherry wood (like a pattern) and is incredibly heavy.
Above we see a few close-ups of the detail. This was added on with bondo. Unfortunately the word "Of" was lost over the years.
Next, is a view of the middle front pattern portion.
Here is a comparison with the production playset front. It also illustrates the size of this piece. With that wood border, the piece is huge and very heavy. I've always dreamed of owning a toy pattern and finding a wood model like this for a key playset is wonderful.