72 air filter housing trivia question

i have 2 air filter housings.
curiously on both:
there is 1 metal and 1 black nylon snorkle mount bolt.
at first i thought my original was rigged, but the replacement i got was the same.
is this typical?
one of the nylon bolts was partially melted. i know this happens occasionally.
so what's original, 2 nylon bolts?
in support of this all washers, nuts and wingnuts are black nylon.
against, the metal bolt is german make and the same 1+1 configuration was on the replacement housing.
opinions?
bob

Both my 72's have all plastic hardware. Seems like a huge coincidence, but I would bet that each at one time has had one plastic one replaced.

makes sense
thanks ed