Hi Alan,
Hope nobody takes this the wrong way, but the 1847 markings are kinda obviously a reference to Barry Storm's version of the Peraltas. (This version appears to be wholly made up from a kernel of truth...at least it's not historically accurate). The 1847 markings, the scratching of Miguel and Pedro into the H/P map, seem to be a tribute to ol' Barry. Or, designed by a scam artist to elicit the attention of his target audience: Dutch Hunters.
I happen to also wholeheartedly agree with DAI, that the ALL CAPS lettering on the stones was not how anyone wrote back then. That style came into being when technical documents such as blueprints and mechanical drawings were being taught in schools, back when you had to actually draw them on a drafting table

Anybody that has been graded in high school or college on their lettering in such documents will recognize the style. In fact, among people my age, I can tell who has had mechanical drawing, drafting, or such classes, just by looking at their handwriting. We all write in all caps, specifically the WAY we were taught to make them, and the way the "8" is written in 1847 is a dead give-away...only draftsmen and the like are trained to write an "8" with two circles one over the other. How people are being trained to write today, I have no idea. But the Spanish never wrote an eight that way, (EDIT: Same thing with the 1, the 4, and the 7) and they didn't write in all caps. At best, they are a modern interpretation of old treasure symbology, which is entirely possible.
Back to the dutch hunters and the stones: Bob Garman gives a story of how the Tumlinsons (Bob and Travis) viewed the stones...or more accurately, how Bob T. viewed the stones. To paraphrase the story, Miguel Pedro Peralta left Santa Fe just ahead of an American military column, taking a road less traveled...he had his own fortune and the Church's fortune with him...apparently the road less traveled was the Gila trail...my guess...anyway, this happens during the Mexican American War (1847). Upon nearing Sonora, Don Peralta buries the two treasures around Queen Creek, just in case he's intercepted by the Americans as he gets closer to the border. (EDIT: Which didn't exist yet)
Not saying any of this is true, but Bob Garmin had a habit of writing down the stories he was told, even if they contradicted each other...which to me kind of gives credence to his work...he didn't edit the stories so they would all make sense together.
Anyway, there's two, probably unpopular explanations for the 1847 markings on the stones.