That's the original version of the the EF 100mm and quite a good lens. As stated, there's not much difference in IQ between it and the 100mm USM, or for that matter the 100mm L/IS. All three are quite good optically.
As a non-USM lens, you probably should not manually override autofocus without first turning off the AF at the switch. To check on this, you might see if Canon has a PDF manual for the lens online at their website or if you can find one elsewhere. But AFAIK, all non-USM lenses need to be switched off before manually focusing, or you risk damaging the focusing mechanism. (USM lenses, OTOH, allow immediate manual focusing iwthout need to turn off AF, which Canon calls FTM or Full Time Manual.) This is going to make the lens slower to use when shooting with autofocus. Of course, a lot of the time it's faster and easier to use manual focus with macro photography anyway. So this likely won't be much of an issue. Non-USM lenses also tend to be slower autofocusing than USM, which will likely be even more exaggerated with any macro lens because they have to move the focusing group so far to be able to focus all the way from infinity to 1:1 magnification.
It does have a focus limiter, though it's not marked on the lens what the distances are. Again, see if you can find a copy of the owners manual that came with the lens originally... that would tell you what the limter's ranges are... I suspect the "limit" setting on this lens allows focus to infiniity and keeps the lens from going into the higher magnifications, while the "full" settings lets it go all the way from infinity to full 1:1. This is the same way the USM lens' limiter works. The L/IS, OTOH, has a three position limiter that allows it to be kept in the close/high mag range, but not able to go all the way to infinity; in a range from infinity to something less than max mag; or covering the entire range from infinity to 1:1.
Note in the photo of the lens, there's no "gold ring" that Canon uses to identify their USM lenses... not to mention they have "Ultrasonic" written several places on most USM lenses.
I forgot that the original EF 100mm was not Internal Focusing (IF). (IF makes the 100 USM and 100 L/IS larger to begin with, but they don't change length while focusing).
AFAIK, that original 100mm also can't be fitted with a tripod mounting ring, the way the two later models can be, optionally.
Oh, and BTW, I believe all three have metal barrels. So that's not a way to distinguish one from the other. The 100 USM is identical in build to the 180/3.5L, in fact.