I'll try to the best of my knowledge to give a short breakdown on the timeline of the different guns.
1. Earon Carter & the Kamikaze Shooters hooked up w/ each other. I believe the very first 3 Comp Guns went to the 2 co-captains (Dave Loo and Tora) and another one of their main Turtle Squad members. We're talking mid 80's here. Before that Earon was mainly known for his work on Sheridan based guns.
2. One of the Shooters took the rail off of his Gold Cup and had Earon mount it on a modified Nelspot. Dave Loo liked the looks and had that same teammate modify his Comp Gun to fit Pachmayer grips for a .45 and also modified his pump handle into a more squarish/rectangular look (like the slide of a .45) and also added Millet sights to his Comp. This was long before Line Si came out with their .45 grips for the Bushmasters. In fact one of the Shooters was still making wood grips for Navarone's Nelspot lowers back then.
3. Dave took the concept of his heavily modified Comp Gun and came up with the idea for the DD68. Obviously Earon had a HUGE influence in the making of this gun as him and Dave were ultra tight. Personal friends off of the field, etc.
4. Soon Dave made more improvements and variations came out including the "Slam Changer" 12 gram changer, "Shorty Duck", "Counter Weight" foregrip, etc.
5. Dave burnt out from running his own field (Shiloh), making the Ducks, etc. basically quit paintball for awhile. Overall I'd generally say 2 years.
6. A Duck-Mag was also built. The first A-M that I&I Sports got was given to a Kamikaze Shooter. (This was even before A-M's were being sold as back then I&I was HUGE and products were often given to I&I for testing to see if they would carry them.) He took a slide for a Duck & also a Duck lower and modified them to fit onto an A-M. He also modified the bottle adaptor to fit vertically in front of the trigger guard. As far as I can tell, this was the first vertical bottled A-M. So the A-M had the look of a .45 lower, with the Duck slide as a shroud over the A-M barral including the front Millet post.
7. SC Village started up a stockgun tourney and Dave built the first 3 "Stock Ducks" from parts he and another Kamikaze Shooter teammate had. A 4th one was soon made for another Shooter. This was 92 or 93.
8. Glen from Check It Products liked the Ducks. Attened the same HS as Dave's son, etc. and got an itch to start up his own company. One of the Shooters had built what would be considered the original "Box Gun" and Glen took that one off original and used it as a template for learning the manufactoring business. Dealing w/ machine shops, working with CAD programs, sourcing and pricing parts, etc. and he came out w/ his own version.
9. Ken K. (Navarone) was working w/ Earon when Earon was still in his Rosecrans shop. Mike R. (GBD) was another employee that the time. Ken took what was left of Dave's parts and started making more Ducks on a piece-by-piece basis. From then on, Carter Machine has put out more Ducks.
10. At the time stock & pump class games weren't hugely popular even here in SoCal so CIP discontinued offering their Box/Super Stocker pump guns. I think it was around 01-02 that they got rid of their inventory of parts.
11. Stock & pump games made a comeback. Redux, Box Gun clones, etc. spring up to support those peeps that want a Duck or Box Gun but otherwise wouldn't have the means to purchase one.
I hope that clarifies some of the history of the DD68. If anything at least it might shed some light upon the different versions and where they fit into the whole category/family of Ducks and Duck clones.