aha
it turns out there actually was a yuma county vs maricopa county
1918 border suit
so the accumulated puzzle pieces now strongly suggest
that it was the arizona supreme court that directed the atwood
survey to do whatever it did in 1918

& that this survey concerned naturally mayu & mayu only
rather than everything south of the santa maria river & north of
mexico
as has been widely presumed

& if this is true then atwood must have had to use his own original
determinations for the mapiyu & mayayu tripoints for his mayu
terminal points

& so the mystery initial monument near lamaya must have been his own
initial as well as terminal monument
& thus actually the 52nd marker in his continuous series

& this was presumably done without prejudice as to the actual
position of either tripoint since it was only a mayu thing

in the case of mapiyu i surmise the original atwood position stuck &
never moved because it was based in the public land grid

which btw on further examination also seems to be the cause of the
jog & yaw beginning at mapiyu too & continuing southward to mexico

but in the case of mayayu aka lamaya
thompson evidently was empowered by the supreme court to establish
the tripoint in 1924
leaving atwoods 1918 initial & terminal rock 50 yards off
& just an oddball & technically unauthorized yet duly marked point
on laya
indeed possibly the only monumented point on laya
if only it still existed

so
just wanted to get that much off my chest
tho there are more new details perhaps best left unreported too
& tho it doesnt bag us a rock solid arizona tricounty point yet
but it has been an education & a trip & possibly even a help