I’ve been noticing some details recently in Gen. Zero, after finishing the game it leaves more time for these things to be noticed.
For instance. On the back of the Radio you can find a little description. It’s written in swedish, naturally, but you can discern some letters here and there.
On another note (pun totally intended), check this out 
On some parts you can even tell the melody !
Regarding the machines, you can serial numbers on them ! And each fuel tank has its own serial number too, changing from type of machine to type of machine not each machine has its own.
That’s roughly 20% of what I’ve encountered until now.