Heres's a general question about the case: What happened to the briefcase?
That is something I have thought about occasionally. This one thing seems to get passed over a lot. Often, it's briefly mentioned that Cooper must have taken it with him and it's with the parachute and/or money and/or Cooper himself.
What happened to the briefcase? Answer: It's still out there! I believe it's somewhere in the vicinity of the placard find and where Cooper allegedly jumped (at 8:13), on V-23. So, Jerry Thomas needs to assemble a search crew, get me help him, and then we need to go look for it, find it, and be forever remembered in Cooper folklore. But wait.....I'm getting a little carried away and ahead of myself.
Reason with me: If he really did have a bomb -- the good stuff that goes boom and kills everybody -- then he surely wouldn't take it with him. He most likely would dis-assemble it as harmless as was possible, then he would chuck it out the back door. If it wasn't really a bomb, just road flares, say, he'd keep the flares (for building a fire and keeping warm in some cave after the landing) and chuck the briefcase -- because it has already served its purpose and it would only be dead weight from here on.
But...what if Cooper took the briefcase with him? He's already got a back chute, the X chute, and a bag of money attached to his waste. He's already bogged down. Question: did he just hang on to the briefcase by its handle or did he wrap his arms around it and hold it close on the jump? Either way, in my mind's eye, he wouldn't have been able to hang on to it. If he was hanging on to the briefcase by the handle, that 200 mph wind would have ripped the handle right off the briefcase on the jump, and the briefcase would go flailing violently into the wind and darkness. If he was holding the briefcase close to his person, same result (I have no data to back up this claim -- I once saw a demo of guy trying to hold on to a pumpkin in the back seat of a car hitting a wall at 40 mph -- it was impossible to hold on to the pumpkin. A different kind of energy here with the jump, but you get the idea -- all that energy all at once -- would he have been able to hang on to the briefcase? In my humble, non-expert opinion, no).
Besides, the well-being of the briefcase would not have been his top priority -- he was more worried about surviving the jump, getting the chute to open, not going into a violent spin, and not losing all that money. So, either way, the briefcase most likely went flying into the darkness, violently thrown about by the wind.
In short, no matter what Cooper decided to do with the briefcase -- chuck it before the jump or take it with him and lose it on the jump -- the briefcase went flying into the darkness, violently tossed about by the violent winds. It most likely occurred somewhere close to the placard location and when Cooper allegedly jumped -- times we know the aft door had to be open and up to the moment he jumped. The briefcase is still out there. I think it will be found some day -- if it's not hopelessly buried under thick briar bushes at the bottom of some canyon -- thereby rendering it "un-findable."
A big to do about not much....
Meyer