This wooden pattern was used to as a foundry mold to cast wheels for the Simpson Lumber Railroad locomotives in the early 1900s. Sand, would be packed around this pattern inside of a casting flask. The sand is then compressed in a process known as ramming. When the molding material reaches the proper density, the pattern is removed. Molten metal is then poured into the cavity created by the positive mold. Once the metal has cooled and hardened, the sand is then broken away and the metal casting is removed.
It is 36" round and is marked Simpson Timber Co. The black and white photo shows the actual train wheel on their locomotive. It is the front wheel.