I think they started frosting/satinating things around '86.
ooops, edited to add, Welcome to the board!

I'm fairly sure I got that info from the history section of the Mdina website, but it has been changed and updated since then and I don't
think that information is there any more.
ok, I've just gone to the site and checked. It has been completely re-written from the original and does not give a date for the use of acid for satination, not any more.

You could always write to them and ask.
https://www.mdinaglass.com.mt/en/aboutus/aboutus/3/our-history.htm#.V2g5RRLpyV9