Well, it didn't take long. A member emailed me offlist that he has a hollow-back faux-lugged stem like the photo Sheldon has added to his website, but marked Milremo. This morning I was changing tires on my 1972 Follis mod 172. It also has a hollow-back faux lugged stem clearly marked PIVO on both sides. So It is now documented that these stems appeared with markings for at least three different companies. I suspect there were several more markings. I also suspect that a single company made them all, although I haven't a clue what company that might be.
Regards,
Jerry Moos
Big Spring, TX