I was responding 100% to the OP as well...if it makes a difference.
At least I learned the word "grok" from this thread! ;)
If anybody deserves some sort of photographic medal it's this guy.
When you refer to a #12 filter, it's a Wratten reference number and is just a bit deeper than a #11 which is your "standard" K2. There's a great deal of information on the filters under Kodak Wratten on Google
I believe coirehogan refers to CC50Y when talking about CC filters.