Here is my answer to this member's question:
A: Dear eBay Member,
As the ad says, this is the "MK I" version, even though that designation does not actually appear anywhere on the lens. It simply means that this is the first version of this model. There were MK II (and possibly MK III and MK IV) versions produced in following years, to replace the original lens. They actually have the Roman numerals "II", "III and "IV" printed right on the lens, usually at the end of the model number. It is a very common practice to refer to the original lens model as a "MK I" or "Mark I" to distinguish it from the newer models.
This is especially true when the original version was actually superior to the new replacement model in some way. Canon sometimes replaces a lens with new model that has been "stripped" of some of the previous model's special features. Frequently, the original one may have had a heavy duty metal lens mount, or a very useful "Distance Window", which were deemed to be too expensive to maintain on the replacement lens. If the new lens had to match a competitor's "price point" to be more competitive in the market place, the "goodies" would be removed to lower the manufacturing cost of the lens. Photography gear is a very competitive business.
However, this is not always the case. Sometimes the newer model will actually be a true improvement over the original. The new model might have an upgraded aperture or special lens elements that make it much more desirable. These important improvements cannot be seen when you take a quick look at the new lens. That is where the "Mark" or "MK" version designation becomes very important.
The only way to know which version really is the "best", is to do a little research. Read as many reviews as you can find to learn exactly which version is considered to be the best value. It will be "time well invested" when you find the lens with the best performance for the money.
Thanks for your great question.
Introduction To The Q & A Guide Series:
I have been answering potential bidder's questions about the items that I have listed on eBay for several years. One kind person suggested that there may be other members who have wondered about the same subject, but may have been too shy to contact me directly. He suggested that it could be useful to post his question, and my answer, for others to see. He recommended that it could be done in the form of an eBay Guide.
This is the sixth in a series of Q & A "Guides" that will be posted.
This series of eBay Guides is based on real questions that were asked of me through eBay Messages, using the "Ask The Seller A Question" feature on my listings. Hopefully, these Guides, based on my actual responses, might provide useful answers to some of your questions too.
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