|P is for Practical|
On the off chance that the oracle might have missed a useful Japanese page I took a swing. Found a very interesting page in Japanese which covers different standards and some history of terminals and codes. Anyway you can probably see the code names in double-width numerals even if you can't read the rest of the kanji. Certainly the MC/Cirrus logos will show up..
Basically there seem to be two major standards in Japan for the magnetic strip, JIS-I and JIS-II. I think this page is from 4 years ago. It says that II was meant for domestic use and I is the international standard, but that II was pretty much scrapped for compatibility.
JIS-I is the same as the ISO standard. Here is a brief translation of this first paragraph for JIS-I.
A. Tracks used and related standards
Note: I looked at www.iso.org and 2894 is withdrawn. 3166 is the country code spec. 3554 is also withdrawn, but is the magnetic stripe encoding spec(?). 4217 is the currency code. Unfortunately it looks like they want you to pay to see the standards (jeez!). I started surfing aba.com (the sitemap) and found x9.com but it is all not very helpful. Hmpf. Maybe they should hire a programmer to provide a credit card parsing service. It is tantalizing but I must be too dense, can't find where the info is.
B. JIS-I type format
C. ISO Standard Industry Assignments(International Credit Card Assignments)
Update: I found mention on the infowar ml about someone who was asking a similar question, and whether the magstripe could hold credit history info. There are machines that say they can parse, according to the oracle, but I'm not so sure the credit companies want people to know what is in there..
Here's a lousy standards-for-sale store at X9: Track 3 Data (for $40) is: - Found it by giving the oracle "www.aba.com magnetic".
Actually that last PDF is extremely detailed, but only a rough breakdown of the central field.