My memory is that these were never placed "to the hilt." Our drilling experience in sandstone was limited to the Garden of the Gods, which was much softer sandstone, and allowed for rounding out the holes as you drilled. But this rock was harder, and didn't allow a convenient hole for the full depth of the pins. So, we tied them off with a sling--and frankly, I think they were in far enough so that these really were reasonable rap anchors when we used them. On the other hand, I do recall thinking that they weren't the greatest "permanent" anchors, either. Still, they were as good as many of the rap anchors we were used to dealing with in those days.
An anchor that leaves a lot to be desired. If we assume these things went into the hilt, then there has been a lot of erosion over the last 27 years. I put in two 1/2 inch bolts, but left these relics for historical purposes.