What a great find! I haven't actually read that specific collection of short stories (we tend to stick to Gallegos's more famous novels and forget about these gems), but the edition looks spectacular.
It's incredible that a book from the 70s is in such good condition; sometimes you're afraid to open them for fear of pages falling out or yellowing, so you were lucky. I completely understand about the font size; it's such a relief when you don't have to strain your eyes to enjoy reading, especially if you're trying to relax.