What is a period correct case for an '73 4001?

[berth]

Someone in the lower countries asked me if a current silver vintage case would be period correct for a '73. But with some searching over here I found a '71 with a black apparantly period correct case. I guess the silver case is not period correct for a '73 then, or is it?

[jps]

Black would be correct.

[heinpete]

With a plastic latch inside to protect the linen where the strap pin of the upper horn is positioned. The body is otherwise not cushioned like in the end of '70ies/beginning '80ies cases.