I have that old Canon 100mm non-usm macro lens. I bought it used for a little over $300 a year or so ago. That lens is build like a tank!
Pros:
- Very well build and feel very solid. Much better than my EF 50mm f/1.4 USM.
- Use smaller 52mm filter
- Front lens element is recessed, no need to use a lens hood.
- Very sharp.
Cons:
- Heavier than the USM version.
- Slower AF (non-usm) but I do not use the AF most of the time.
- Not internal focus, so the front part of the lens will extend.
- Manual focus via a switch. I like full time manual focus like my EF 85mm f/1.8 (but I use manual focus most of the time, so no big deal)
- Hard to clean the front lens element because of it position locates deep inside the lens.
Assuming the lens you are going to take a look is in good working condition, so if you get a used EF 100mm USM macro lens instead of the older one, you pay about $100 for better AF and internal focusing (IF). I choose the older version because I really don't care too much about the AF and IF since I am going to use it for macro stuff anyway. If you also want to use it for portrait lens, the USM version may worth the extra. By the way, the AF is slower, I do NOT mean the AF is sloooooooowww.
Here are some sample shots with my old 100mm Canon lens.
http://www.thephotoforum.com/forum/...-took-another-fly-shot-afternoon-closeup.html