I would ask for a bit more information...
What are the names of towns in close proximity to these rocks?
What type of rocks are they? Sandstone? Limestone? (They appear to be limestone based on the photos, but sometimes lighting can mislead you.) Oklahoma has lots of sandstone, but judging from the photos (which appear to be limestone) would place the location just about anywhere except where the sandstone prevails. My guess (probably wrong) would be southwest corner of the state, but what do I know?
What are the names of some of the famous saloons in the area?
Do you have any additional information which may be helpful?
The markings show 1955 and 19 over 55. Could these be dates?
It could be as simple as two people trying to make their mark on the area with no real treasure involved.