I've seen the same thing. The 1/4 corners were established on different surveys from different sides and are about 100 feet apart. At least they both land on the line between the section corners.
This thread has brought out several examples or reasons that two corners might exist. None have suggested why a surveyor would set two.
He does note in other places "found nail, replaced with iron and cap" so I'm pretty sure he didn't find anything here or he would have noted it. I'm going to believe the idea of double notation for one corner until I find otherwise.
Bill93, post: 339295, member: 87 wrote: I guess I need to go to the courthouse and find the corner records - they don't seem to be on line.
I convinced myself I was looking correctly on line, so I contacted the surveyor. He replied today that - oops - the corner records were still in his file (since 2012) and now he has sent them in. So after a few weeks I will look again and maybe verify that there was only one quarter corner, as I now think it is.