What is a 'Special Six'?

Thanks all. This is not in the description sections of Chilton's but in the specs which was reasonably on the mark in those years. The Special 6 t has it's own engine code per Chilton's: C for 68-69 and E for 70. And the 170 and 198's are listed with different engine codes so that is not it. This list has all the other engine codes you would expect like the HP variants, and so forth, so it seems accutate enough to think this is legit. Maybe it just never really got ordered.....??

And per the Allpar site, 1960 had the HyperPak option, so again, maybe this was a real spin off. I gotta find my old Direct Connection catalog from the day and see what is mentioned in regards to /6 variants.