Dave is correct, the W in a circle is the Westinghouse marking. That means you have a WWI period bolt. I am puzzled by that number though. It looks like a drawing number sequence, but there are two inconsistencies. First, Westinghouse (and other WWI mfgs) did NOT put drawing numbers on any of the parts. All patents were on hold to keep the specs out of the public domain until after the war. Second, that number does not match any I have seen for a 1917/1919 bolt. The WWI numbers were a totally different sequence too. That is a puzzler! Can you post pics?
Sorry Lucky no camera. Woody