The O'Neill machine Strange Mould Seams from El Paso, Texas
Sandra Ratch, M.A. April, 2022
I do not want anyone to think I am criticizing Bill Lockhart or suggesting that he has not contributed greatly to the knowledge of bottle making in the 20th century. On the contrary, without his work, we would have little information to go on. Here, I just think I found a better theory to explain this strange mark on the bottom of this bottle. (Bill Lockhart has read this post and agrees with what I've found).
In 2010, Bill Lockhart described a bottle found in El Paso that had an odd mark on the base (https://sha.org/bottle/pdffiles/EPChap7b.pdf, p. 252, Figure 7-23). You can see that the mark is two concentric circles, offset from the bottle and at 1+ cm apart from each other. At the time he could not attribute a machine to the making of this bottle.