The 5/8 by 9/16 T-1917 wrench is the only one I've seen listed in the tool kit inventory. I have several of the 1/2 by 7/16 wrenches and wonder why they were not included in the kit. This wrench doesn't have a p/n embossed on it like the T-1917. While there are several places to use the 1/2 end, the only place I see a use for the 7/16 is the spring clamp nut. Just wondering.
That is because it is a Model A tool.
I keep one in my took kit, even if it is for a "modern" car.
A 1917 wrench is 11/16" on one end, and I'm not sure what size the other end is. It sounds like you have a V-8 wrench to me, or as Uncle Jack mentioned, maybe a Model A.