Mac plus copper inside

[marchintosh]

Hi everyone, I bought this Mac Plus in Sweden, and inside I found this copper mask. My idea is that it was installed to prevent interference with other equipment; it was in a lab at the University of Chemistry in Gothenburg.
Do you agree?

 

[Byrd]

Yes it looks like some sort of enhanced RF shielding - see "Tempest" Macs of the same era. Is the mask handmade? It's probably worth a bit noting copper prices nowadays.