OK. I got the catalog from 1930. What you have is a "GW-1 Special Wrench (case hardened), for changing charging rate on all Ford and Liberty generators as used on Ford cars." Quote from catalog #9, Gilfillan Automotive Replacement Parts, Manufactured by Gilfillan Bros., Inc., Kansas City, Los Angeles, New York, Oakland. Retail price, 50 cents, 25 cents wholesale.
1939 has the one I ran across last year.