From the Sigma website:
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Q: What are the differences between the 70-300mm F/4-5.6 Macro II and the 70-300 F/4-5.6 APO Macro Super II zoom lenses?
A: The major difference between these two lenses is the optical performance. The DL Super
model features a more conventional, achromatic optical design and uses one element of Special Low Dispersion glass (SLD). Its sharpness and contrast are rated very highly, however it is not quite as good as the APO Super
model, which uses an apochromatic optical design and uses three SLD glass elements. This
model has been top-rated by independent photo magazines. The APO Super
model is also somewhat more expensive than the DL Super
mode. If you plan to make very large enlargements from your negatives or slides, the APO Super lens may be your better choice.
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I have the APO II
model, and it has a red band, but to make it even easier to figure out which
model it is, it has APO written on the side. I guess the "APO" stands for apochromatic, resulting from the use of the low dispersion glass elements.
The pictures on the site are a little unclear, but it looks like the DL
model has no coloured band.
Cheers