There are likely many but here's what I know of. In addition the the variants that you mentioned the CQC-6 was also made with bead blasted, mismarked blades. These variants were unofficially dubbed the "6/7" in order to differentiate from other CQC-6's. These knives which numbered less than ten(?) first appeared at the NY Knife Show last year. Ernie did personally assure the Forum members that despite the logo mistake the blades were in fact ground by him. Check out Ernie's discussion on the topic here:
http://www.bladeforums.com/ubb/Forum16/HTML/000143.html
There is also a right side grind CQC-6 of which Ernie says there is only one.
I would not be surprised if there are other custom orders of CQC-6's with some interesting options particularly those ordered by SOF personnel.
The Japanese market has seen heated Emerson collecting. So much so that Ernie has made some true "variations" on the CQC-6. These are hybrid knives specifically intended for the Japanese market which incorporate the mating of a Viper 5 style blade with a CQC-6 handle. Pictures of this hybrid along with a damascus Commander can be found in this month's issue of the awesome Japanese magazine KNIFE.
Finally, there are many subtleties regarding various generations of CQC-6's. These are usaully refered to as "bells and whistles" and would require a much longer reply to describe in any detail. Check out JBrovo's reply at this topic here:
http://www.bladeforums.com/ubb/Forum16/HTML/000287.html
Other Usual Suspects like Tamishigiri, JBravo, Nyeti, J Hollister, Fenris, Jackstraw should know about any other CQC-6 anomolies that I never even dreamed of!
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Usual Suspect
http://www.freeyellow.com/members8/arkhamdrifter/index.html
[This message has been edited by arkhamdrifter (edited 05-19-2000).]