I remember the same exact toilet from my first backpack in the early 1970s. It was at Pear Lake, also in Sequoia National Park. It was new at the time (fresh wood), so my guess is this toilet was built about the same time, so would be about 40 years old.
I found it kind of lacking in privacy for #2

. Especially in Pear Lake where the toiler was in the middle of a boulder field slightly above the lake.
Pear Lake has since replaced the simple "open" toilet with a complex of 2-4 "Clivus Multrum"(sp) composting toilets (I guess is Pear Lake receives a lot more use now).