Just guessing that this tool is automotive related. Anyone recognize G & K marking(I know its out of focus but thats what is stamped on wrench) Six point box is 9/16. Big heavy screwdriver is 9/16 wide as well.

first guess was distributor wrench, but that's not it

brake work?  wrench and adjuster?


cant get much purchase on a 9/16 if its only 5 inches long


dunno about G & K


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The only reference I could come up for for G&K was someone related to Gilbarco (The folks who made Gas Pumps), and it is very suspect :(

Reminds me of a tire iron wrench, but it's awfull small, motorcycle?

I worked for a major oil company in the 90s.  Started a joint venture with wally world.  I had responsibility for company owned convenient stores coming out of the ground into their first few weeks of opening.  Worked exclusively with Gilbarco and their pumps....including regular visits to their factory in Raleigh/Durham.  I've seen a lot of service on Gilbarco pumps, but I've never seen this wrench or any G&K markings.

Just looking at the patina, the shape of the screwdriver end,  am betting this dates to the 40s or before.   A super short 9/16, with screwdriver to me smacks of a special wrench for setting/adjusting something.   1930s gas pumps perhaps?   Am having a thought on drive belt adjustment on one of the early electric pumps.