I was paying attention to this stuff by the turn of the century and best practice back then was the same as it is now. Screen readers have come a long way, but they could handle empty alt attributes correctly back then as well. I just checked, and the HTML 4 specification has been advising people to use empty alt attributes in this situation since 1997.

https://www.w3.org/TR/WD-html40-970708/struct/includes.html#...