I found this today. Maybe some of you all have also seen this before. This is a very comprehensive list of everything Marble sights related, company history timeline at the top, catalog information, application codes and when specific sights were cataloged. Wish I would have found it sooner as it answers a lot of questions I spent a lot of time answering/trying to answer myself. A few of the dates differ slightly from dates in their own catalogs, not sure why that is, but they appear very close to the same.
http://www.marblearms.com/pdf/GunSightsBook.pdf

I added the link down at the Model 1894 sight page along with another project of Marble advertising history that was also compiled in 1998. These guys compiled some really informative stuff in my opinion.
http://www.marblearms.com/pdf/VintageAdvertisements.pdf

Over in the History part of their website is another neat history of all of their other products.
http://www.marblearms.com/index.html

If anyone wated to know roughly when a Marble sight was available on a particular Winchester, I think this would really help.

Brad