As the reason I posted was I had no info on what this is other than it is a wrench and cast into the handle is clearly B.G. SPARK PLUGS. Is it a spark plug wtench?? Don't know. Is it for aircraft? Don't know. After reading the above posts that the "common" aircraft spark plug is 7/8" I second guessed myself, I did go to school in the California Public School System it wouldn't be the 3rd time I was wrong. In the attached pictures you will see I checked, double checked and tripple checked. I used a Made In USA machinist rule, a Huskey socket of questionable manufacturer, 12 point as the wrench in question appears to be 12 point but in all honesty I didn't count, a Made In USA Dayton Combination Wrench and a Made In Sweden Vernier Caliper. All measurements/checks were conducted with a vintage castle nut. At this point I am now pretty sure it is a 1" wrench so if 7/8" is the common aircraft plug size and this is a plug wrench it is either very uncommon any very valuable or its just a 1" box wrench...