Real cool case, had one like it for years, had to let it go just this Spring to ship a real expensive SG ($1600). Also had an original Vox case in the same shape back in the 90's and it did fit my '59/60 Strat like a dream, and the cool thing (two things actually) is that it was not instantly recognizable as a Fender case so people had no idea what was in it - and that can be a good thing - also took a lot less room in the back seat of the car, easier to hide from "prying eyes"...
The Guild branded one is a great score for someone who wants to complete a vintage Guild, my guess would be for a vintage S-100, definitely not one of the crazy 80's guitars, and it's too thin for a archtop.