I got a ton of FD lenses from my grandfather. Strange thing is, they are pretty much all macro. The one that confuses me the most is a Sigma 28mm macro lens. What specific use would someone get from a 28mm macro? I expect you would have to be really close to the subject. I think he liked to shoot flowers, so maybe it gave him the ability to focus closely on details of the flowers while being able to get more of them in the shot?
I'm using it as a regular 28mm prime lens right now. It focuses fine to infinity and is actually a lot of fun to use.