How can cores of two different diameters be sitting in one and the same core box? That looks a bit odd, but there is an explanation for it.... Read here: https://lnkd.in/eDGSyNun
If that piece is a perfect cylinder (squared off ends) then indeed it may have been "overcored" in the lab and used for whole core analysis. The lab maybe didn't have coreholders for the full core size. The rock is far too hard, the diameters too consistent and the diameter difference too great for other rational explanations. In MHO.
Coring Consultant - U.S. Land
11hI've recovered different diameter core many times when the formation properties change and sections wash out to various degrees, after which full gauge core is captured making it possible to recover the undercut sections.