Sarah Jones answers:

First off,congrats & bravo for saving such a sweet looking,and much misunderstood dog. What a looker!
Definitely looks to me like someone put a Staffordshire head on a Boxer body,especially with the elongated ribcage and those long legs. Staffordshire’s are generally shorter, more “squared out” dogs,while Boxer’s tend to be taller and longer. And since my Staffordshire boy has recently fathered a Boxer cross litter [accidentally I assure you!],I’ve got a good idea of what your cutie looked like as a puppy.
And before the overbreeding flaming starts,let me just say -my boy was in MY yard when my neighbor’s Boxer bitch came to him,and since he’s a show dog,neutering him would automatically disqualify him from the show ring. But all the pups got great homes,we saw to that.
Regardless of what she turns out to be,train her well,and love her well. Blessings!