Here's a "modern" package of hinges I bought a few years ago that I thought were standard folded hinges, but when I opened the package they were unfolded. (So the unfolded ones are still out there!)

I'm still using them up. In fact, I group about 10 or so together, fold them and then take a pair of scissors and cut them in half to double the number of hinges. I'm working on collections of older precancels, so I'm not terribly worried about hinges damaging the stamps, and mounting them looks so much nicer, and is so much easier than going through hundreds of glassine envelopes.