It happens that I observed on Ebay that Executive Skylines are selling for much more than "regular" ones. How many kinds of Skylines are known and which are the differences between them?

In addition to the myriad of cap style/color/material combinations, there are three sizes: Demi, Standard, and Executive. Executive pens are rare (!) and very desirable; hence, they command very high prices. I've worked on only two of them in my career (so far), and I don't own one.

Thank you Richard for your explanation. Here is an auction for an executive Skyline, it is interesting to see how high will go the price.

I've got an Executive. It's hard to believe that a hack like me would have a pen that Richard doesn't yet.

Oh well, score now 10,000 to 1.

I saw/held one at an antique store once.
It was in a ZipLoc bag with a bunch of other pen stuff.
The owner claimed that is had "belonged to his Uncle" and wanted me to make an offer.
When I asked him what he wanted for it, he got had and said "No, its not for sale!" and put it back in the drawer he'd pulled it from.

Oh well

The one linked to above went for $330, which surprised me, given that wonderful looking nib. I've seen them fetch considerably more on eBay.

Dan