When did J&B Scotch switch from corks to screw-tops? A friend of mine has come into possession of some rather old alcohol.  On one bottle of J&amp;B Scotch, the label looks like this one from 1958 and not any of their later ones, but my friend's bottle has a screw-top cap, not a cork.

When did J&amp;B start using caps?  (There is no contact information on their web site to ask them directly.)
From what I can find I'm not sure I can give an exact answer to the main question (when J&amp;B started using screw caps) but I think I found something that matches your description, from 1972:

https://www.maxliquor.com/product-p/j-and-b-scotch-1972-quart.htm



As far as I can tell the label matches the picture on the page you linked and appears to have a screw-cap.

Also, on the website you linked to, there are example bottles from the 60's and the 70's.  Interestingly though, the 70's bottle has a different label than the one above from 1972.

Given all of this, I would assume the switch to screw caps happened in the late 60's or early 70's and that the bottle your friend obtained is likely from the same time period.