Some photo finishers might try to take a "snap" from 1944 and lovingly take the creases and folds out of the image and restore it to pristine condition. Some may even apply a faux hand tint to it to make it look like someone did something special to it 66 years ago. I sort of went the other way on today's image. I took a shot from a reenactment demonstration last summer and tried to make it look like it had several decades of being carried around and then had been tossed into a drawer to be forgotten. I probably need to do a little more work (probably start over with the original) to get it looking aged. The "cracks" need some work. They need to be rougher and have the emulsion look like it's separated. The edges of the "print" need to be more distressed and the overall image of the image needs to be discolored. I print isn't going to sit in some GIs wallet throughout the war and then survive in a drawer without getting pretty well damaged. It's not bad for a first attempt, but if you're interested in how I'll address the next round, hit the "read more".
The first thing I notice is that the conversion to B&W has to be better. The image of the print is pretty muddy. Of course, since this is supposed to be a "drug store" print, it probably shouldn't be a really snappy print with good contrast. Maybe muddy is more authentic, I'll have to think about that for a while.
Step two will, most likely, be the cracks. Any discoloration would come after the cracking because the bare paper that would show up in the cracks would be discolored too. The plan for the cracks would be that the photo had been folded to fit into the GIs wallet, so most of the cracking would be in the center. A stray crack might run counter to the majority, but only one or two lines will do it. The big deal with the cracks will be giving them some dimension. It has to look like you'd "feel" them if you ran your finger across the surface.
For the discoloration there's a couple of ways to go. The first thing would be to choose colors for the effect. Maybe a foreground of a coffee color and a background of a Campbell's Manhattan Clam Chowder broth hue. The using Photoshop's Render Clouds filter and stretch and blur the clouds until they look like blobs would be a way to go. Changing the blending mode and lowering the Opacity could be the way to make it believable. Stealing a trick from Bert Monroy to add some dirt would close that portion of the project.
That's a short snapshot (bad pun) of the work that needs to be done. Sounds to me like a good project for a snowy day.