Davis & Cook Level Restoration.
The level is designed to lay on one side, so at the top of the wood is marked “TOP”, so you have one surface for both plumb and level.
“MANUFACTURED BY DAVIS & COOK WATERTOWN N.Y. U.S.A. COOK’S LEVEL PAT. OCT. 20 1903”
http://www.datamp.org/patents/displayPatent.php?pn=742010&id=41885
http://www.davistownmuseum.org/bioJackson.html
