That second listing is indeed AI converted. it may or may not need a cleaning (dust in a lens usually has little effect), but even so, that's a pretty nice lens for the price. The codes on the lens suggests that it might not have the most advanced coatings (Nikkor P, vs PC), but based on the serial number, it may. Not a big deal either way.
This lens has been converted using the Nikon AI conversion kit, which makes for the best possible conversion. This lens, while having the same optical design as the AI and AI-s lenses was the first version and came without multicoating that first appears in the P-C version. This lens isn't chopped liver, but a later version, an AI'd P-C or an AI or AI-s lens would have the best coating. The AI-s version also has a built in hood which is a nice feature.
Left to right: 105 f/1.8 AI-s, 105 f/2.5 P AI'd, 105 f/2.5 P-C AI'd, 105 f/2.5 AI-s
The P lens has a different optical design than the two on the right. The f/1.8 lens on the left has a different optical design and because of its speed is quite a bit more expensive than the other two.
The price listed for the P in the E-Bay auction is not bad and my guess is the lens will give you fine performance. My P lens, and earlier version does not have the latest coatings either but it produces some lovely images. $109 is not a bad place to begin...
Smiert's description of the back of the lens is right on. Nomenclature and even descriptions can be mistaken, but looking at the back the lens as well as the side where the aperture nuimbers are printed will tell you what is going on. Lenses converted with the Nikon AI conversion kit will have a second row of smaller aperture numbers at the very bottom, as does the lens you refer to above that sells for $109.
I see Smiert got things started here, again with thorough and accurate information. This isn't rocket science but a bit of research definitely comes in handy.
It doesn't have the built in hood but it looks like a lovely lens and comes with a separate lens hood. It has a couple of days left before you reach the end of the auction so there is no telling what the lens will sell for. And if you're going to be bidding in auctions, I'd advise you to do it through a third party service, commonly called "snipe" services. For a very nominal fee they will track an auction for you and place a bid up to the maximum you select right at the end of the auction. Keeping track of an auction and bidding at the last moment is a royal pain in the butt.
I use Esnipe to place bids on my behalf. Of course, before you use such a service, you have to get a sense of what prices are for a given item and decide how much you're willing to pay. What you don't want to do is get into a bidding war that keeps pushing prices higher. If you lose one auction, you can count on the fact another copy of the same item will show up. This is especially true for lenses like the 105. Hundreds of thousands of these lenses were made.
Also consider the 85mm f/1.8 G AFS lens. I't not as fast as the f/1.4 version, but it is a really nice lens. I like it much more than the AF-D f/1.8 version. On an 85mm lens I don't miss the 1.4 aperture, and usually stop down to f/2.8 or 4 for the increased depth of field on portraits.
