All About Pocket Knives

Parker's Price Guide Vol. 8 lists several different XX USA (1965-69) 5488 prices. The basic "USA USA Big Congress" mint price is $800. In addition, he has the "5488 XX USA" at $1850 and the "5488 USA XX" at $1850. Just wondering if I can get some help in understanding what these designations mean. How can you tell and what should I be looking for? I've got one on Ebay right now that I assume is a basic 5488, and I expect to sell a couple more. But the range in value from $800 to $1850 is significant, and I don't know how to tell. Any help and insight you can provide is appreciate.

Here's the link to my current listing:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0347353142

Let me start by saying that I do not speak for Tony Foster, but I believe that he intends those higher vales are for "transition" knives...on a four bladed Case congress, the two larger blades will each be tang stamped. Sometimes when the stampings were changed over, they used blades of different stampings so the knife is referred to as a "transition" knife. So a 5488 with the XX stamp on one blade and the USA stamp on the other is a transition which is rare.

The XX-USA and USA-XX refers to which of the two large blades has which stamping.