I remember that a number of older (80s to maybe mid 90s) zooms had a "macro" mode where you would throw a switch that allowed the lens to focus closer. What was that? was it just a built in extension tube or something more complicated?
Here's a quote describing the Tokina 28-85/3.5-4.5:
"I have recently discovered that there are two versions of the Tokina. I have the earlier one. The earlier one has a narrower zoom ring than the later one. With the earlier one, you enter macro mode by pressing a button and turning the zoom ring past 85."
Source page is http://lists.tako.de/Olympus-OM/2003-11/msg01595.html