Here is my theory:
If you look at the one auction picture, you can see the most used one is the "prototype". Also, the auction is from Massachusetts. That means there is a darn good chance this person may have either worked on the line or worked for Gillette. Given the use of the prototype razor, including the amount of soap build up, perhaps this was a prototype like the current iPhone 4g, that they let employees use and test, to determine if it would be a good idea/sell well. While it might not have been good enough for production, the people liked it so much, they kept using them.
OR
The slotted comb instead of open comb violated another companies design patent, which prevented Gillette from marketing it.
I contacted the seller--the person who owned these razors worked for Gillette for 40 years.