I bealive it was the k3 master system came in a black box now that i see all the sets, there is a size difference compared to the others, i got free money for lowes so would rather just trade even steven...
Well my k3 is blue . I have both and they are the same basic size and color. In fact my guide block came off the k4.
The relative size of the jigs are within an inch of each other so I personally can't see trading for size . Maybe the k2 since it is made of aluminum may hold up better but in that case there are sources out there selling k2 in new condition for the less than the current k4 and coming k5. Summerfield who is big in high end router tables and bits and accessories for one I been told they are related to the original kreg designers. I believe maybe even Harbor Freight they look like k2. I don't own a k2 so I cant say for sure. Also if your interested the router forum is also good source of help for woodworkers very knowledgeable people there on routers, jig, and tables. Here is the link enjoy.
I use to be an active member (still a member, not active on it though) of the Router Forums and had downloaded a lot of their videos and enjoyed watching them. I wanted so bad to make me a router table like theirs and build stuff, but never did.