Trailer loading/unloading and ride home were fortunately uneventful. It's a 25" deep box, comparable to the current 6S double bay boxes from what I can see. Also came w/a Matco cover, about a dozen unused Matco and SO socket rails, and a few torque wrenches. I swear pictures of these size boxes never do them justice, they are so much bigger in person. Thanks for the help and kind words guys. It was a guy's personal home box. If anyone was wondering, it wasn't a CL find, the ad was posted on a Facebook local "online yard sale" page of all places, usually consisting of countless ads for baby stuff and crappy furniture.
After a quick wipe down and a coat of wax: