This is a wonderful item. It is an original Calumet Baking Powder Butter and Eggs sign. It was used by store owners to display the price of their wares (and advertise for Calumet at the same time). You've probably seen the metal reproductions, but this is the real deal. It is made of cardboard or thick paper, and has the price adjustment wheels mounted on the back. Measures about 14 1/2" x 11".
While there is some yellowing of the paper , mostly around the edges, we consider it to be in excellent condition for the age. It would have been made sometime before 1929 since that's when General Foods bought out the brand.
All that being said, a member contacted me and told me there were cardboard reproductions similar to this made in the 1980s. I have looked closely at this item and here are my findings.
The printing is lithography or perhaps screen printing. That is, it's solid blocks of color, not printed with dots like you would see with a 4 color press, inkjet or laser printer.
The staining appears to permeate the paper and not simply be applied. Also, the staining covers everything. In almost all the cases of fake stains, rust, etc. I've seen, they only bother to stain the front.
The paper is not simple posterboard or paper. It almost looks like fiberglass when you magnify it.
The grommets to hold the paper reels and to hang the sign are made of copper (or perhaps brass), not steel or aluminum as would be found in newer manufacturing.
In summary, if this is a reproduction, they have gone to counterfeit money levels of detail to make it look real. I consider it highly unlikely since the member said the reproductions were sold for $3 back in the 80s. I've added a few magnified photos to help you judge for yourself.