I'm pretty sure Space Shuttle was one of the first WMS with a folding
head, but I'm not 100%, if it was first. Also, the early WMS folding
heads had no latch at all, and the non-removable speaker panel. You
really have to watch out when you bolt these together. Especially, if
you are expecting a latch!!!
Oh, and to add to the list, I believe Super Orbit in '83 was the first
folding GTB. This would have also been the first "standard" width GTB
game in awhile. Also, SO was the first to use the narrow head and
cheaper cabinet package.
Jim
Bally heads around Flash Gordon-up fold on hinges. Williams heads
around 1986 started folding.
No classic stern heads fold down on hinges.
Only DE/Sega/Stern heads use the hex wrench method - the others use a
latch and bolts to hold the head in place (latch initially to hold it
while you bolt it in - DO NOT use only the latch!)