Rebar, Planted White Stone, and 1877 Stone Mound?

So, one of the tasks for the day was to look for the NW corner of the 164.3 ac. Lot 18 shown on the 1877 subdivision plat below.

This corner of Lot 18 is also shown as being the SW corner of a certain 507 acre tract conveyed in late August of 1877 to a woman named Mrs. Albertina Steussy.

In the deed of conveyance of the 507 acre tract prior to the late September, 1877 date of the subdivision, the SW corner of the Steussy tract is described as being marked by a "stone mound for corner" in a location that was most likely then prairie.

In 1938, a well-respected Austin surveyor reported finding a "set stone" at the corner and noted in his private records that he thought it to be the original corner.

I went to the angle point in an old wire fence that looked as if it had been built before 1938 and that mimicked the angle shown on the 1877 plat to see whether the set stone was still in place. In part, this was to see what the stone looked like, and in part to get a survey tie to it to see how it fits into the overall pattern of boundary reconstruction.

The angle post looked promising, a very old cedar post that I'd guess was 1920 or earlier vintage. However, about a foot North of the post was some fairly fresh ribbon on a 1/2 in. iron rod of no great age. No set stone. No stone mound.

In less than a minute's work with the tile probe, however, I was making contact with something that felt like a stone about 10 inches down. Some root cutting and dirt shovelling later, there was in fact the top of a piece of 3" x 6" chalk limestone that is the material for a textbook set stone in that black clay soil where such stone isn't natively found.

The set stone was leaning NW'ly, so part of the work was plumbing it up and getting it firmed up in that position. Apparently, the roots of a hackberry had pushed it over a bit.

The fact that there's a modern rebar about a foot away from the 19th century stone isn't particularly interesting. Stuff happens. What is interesting is that the original deed in August of 1877 to Mrs. Steussy had called for the mark as being a stone mound and the piece of chalk limestone hardly qualifies as that. So what is the status of the chalk limestone that the 1938 surveyor had thought to be the original corner?

An 1892 metes and bounds subdivision of Lot 17 just South of Lot 18 calls for each of the corners of that lot as being marked by "a planted white stone" and describes at least two of the white stones as original corners of the lot. Considering that the parties to the 1892 conveyance were Campbells, apparently members of the 1877 surveyor's family, there is probably good reason to think that he had made the 1892 survey that cut the lot up. If so, he would have probably recognized the marks that he himself had left 15 years earlier.

The upright piece of chalk limestone 3" x 6" x _" certainly fits the description of "a planted white stone" perfectly, but where is the stone mound?

Since 1938, at least 10 inches of soil have evidently built up at that corner, burying the stone. Possibly as much or more soil had accumulated at the corner since 1877, so I suppose that there is a chance that the planted white stone is actually in the stone mound built to mark the SW corner of the 507 acre Steussy tract, only now about 20 inches or so below grade.

In case anyone is interested, I'll take a photo of the rebar, stone, and any mound when I go back to actually locate the stone and to do a bit more digging to see if a mound is there as well.