they are both flat backs.
the "browner one" with the Westerly trc, bridge and pick guard is 1972 and just says "D-25."
the other one with Hoboken trc, bridge, and pick guard (and serial number) is 1970 and says "D-25 BR." on that one the back center brace is not visible in the above photos (but it definitely exists!!)
exhibit A:
to answer the backpacking question, it has been a while since i've done any over the summer but I used to do a ton. these days, most of my free time is in the fall and winter. still outdoors plenty, just mostly skiing and sometimes even a backcountry hut ski trip which can sometimes be pretty hard core (but have only done that a few times)- ridgerest/therma rest has definitely saved me many times on those excursions, great for guitars too!