I've included a photo of that maker's mark below, but note that it reads: Form No. This billboard was never hung up, and was stored in a bowling alley storage room for nearly 80 years until a several months back. The billboard was in was once owned by Schlitz Brewing and used as a beer warehouse. Old Milwaukee was owned by Schlitz during that time period.
Some may want to restore the sign, but I think it shows honestly as-is. Note there is some flaking and loss of paint along the bottom from moisture, but the wood frame and supports, which are usually rotten, are beautiful. I've never seen anything like this and it would make an outstanding rec room, tavern, barn, or mancave centerpiece. The item "Vintage 1930's Old Milwaukee Art Billboard Metal Tin Sign Schlitz Beer Americana" is in sale since Thursday, August 8, 2019. This item is in the category "Collectibles\Breweriana, Beer\Signs & Tins\Other Beer Signs & Tins". The seller is "tiedke" and is located in Cross Plains, Wisconsin. This item can't be shipped, the buyer must pick up the item.