Function of these left-over mechanical parts? (HP 8590/91E)

[Greybeard]

I found these parts in a separate plastic bag taped on the back of an HP8591E spectrum analyzer, they seem to be left over from the previous user's last repair attempt.

Maybe one of you know the function or position of the parts in the device.

For size reference: The screws have M4 threads (5/32")
Material of the rectangular parts: looks like aluminium, but zinc or magnesium is also possible.

[AndrewEp17]

It's possibly for mounting a heatsink to a component. Maybe the previous owner replaced a transistor or something with a different package and it didn't fit the heatsink. Or they just had parts left over and didn't want to take it apart again to put them back haha

[Greybeard]

Or they just had parts left over and didn't want to take it apart again to put them back haha

Exactly, that's what the user said.

Maybe the previous owner replaced a transistor or something with a different package and it didn't fit the heatsink.

No, he just opened the case (he said)...

[m k]

Maybe structural something for plastic, where final pressure is between irons.
And behind a corner since left out.

[Greybeard]

Finally I found out it's the rear foot spacers: