antique block & tackle with cast iron double pulley, rope & pulley barn hoist

Antique block and tackle with a cast iron double pulley and locking mechanism. This block and tackle hoist is rigged up with a natural fiber rope (hemp or sisal, we're not sure).

The cast iron locking pulley assembly of the hoist is about 6 inches long and takes a 1/2 inch rope. The lower pulley block of the hoist is steel with old paint.