Somebody was mentioning on here (tnet) how it makes no sense why there would be so many markers back to treasures (giving the treasure spot away) so I thought I would address this, First there are thousands of vault caches across the country, so how exactly would you go about marking this many caches?
Would you put a little carved sign on some obscure cliff face somewhere? That might work if you are the person who put it there and are the same person who is going to come back to retrieve it.(because you know the land and where to look)
But what happens when you live in another country and you have to send your relatives back to retrieve the cache who have never been here before, even with a map there has to be something they could follow (landmarks) and since there were no real roads at the time in the places these treasures were hidden these landmarks better be pretty good, and all natural markers are really not the best markers (no way to know if they are the correct markers on the map), so man made strategically placed markers need to be made in order to verify the way in to the treasure (lets say turtles owls vertical lines singular lit up boulders below peaks etc.) remember there were no Odometers back then for distance (I know lots of people who get lost today even on a highway with signs)
So after getting to the treasure site what do we look for (something that stands out that is not natural) No matter which way you look at it, there is absolutely no way to find a treasure without at least 1 man made marker onsite even with the map (since the map has to go from at least 1 Marker to the cache site)
Now for the Problem 1 Marker on a Boulder or cliff face can be destroyed,(which happened when slaves and Indians revolted) so why not have multiple markers go to an invisible spot that they could go from to the treasure entrance which would be very closeby this well marked invisible spot.
This way the invisible spot would be easy to find, but at the same time it would be impossible to find the treasure without having either (secret knowledge or a map) from this well marked invisible spot, this way multiple markers would have to be destroyed in order to lose the invisible spot and you had to have a map or secret knowledge to find the treasure entrance from this Invisible spot which would be very closeby (lets say within 50 feet of the invisible spot)
Seems pretty logical and ingenious to me.