Thanks,
I went over to BobTheOilGuy, whew, days of reading there.
Also found Nodia.com, more reading.
Tried google on "ISO Cleanliness Codes (or Standards)" and you will get a ton more information. A lot if it is for hydraulics, but a good bit for engine oil also.
I found there is an old ISO #/# that was 5um and 15um. There is a newer (1999 I think) #/#/# that was 2um, 5um, 15um and that is changing to 4um, 6um, 14um within the last couple of years because the standards material used for the 2um for calibration is no longer available and apparently was not particularly stable.
For the bypass filter crowd, industry has been doing this for a long time and has A LOT of options. Most of the industry stuff is certified absolute at xxxum. I bet pretty pricy though.
Thanks for the help,
Bob Weis