This a Specialty Service Tool BX SST 2091 Mfg. by Toyota for the US Military for use on 2 1/2 Ton 6x6 Cargo Truck and a 4x4 Weapon Carrier . It is part of Kit "B". It's a "Wrench" for the Spring U Bolt Nut . The #23 is on one end and #26 is on the other end .
I've taken a picture of the tag on the box which shows the # and the purpose of the wrench 
If you zoom in you can see there is no visible evidence of it ever being used

Please ask all questions prior to purchase as I do not do returns