Directory Spy

I was thinking about a simple directory classification code, which gives you a quick insight into a what a directory is in just 2-5 letters. This saves advertising space, and allows submitters to understand characteristics of a directory at a glance.

e.g.

0 to 9 = the Google Page Rank of the directory
G = General, N = Niche
R = Need to Register, E = Express (i.e. no registration)
F = Free, P = Paid, R = Free Reciprocal link if no free link.

e.g. Ickle Directory is a paid general directory with PR4 and no registration: GEP4

A niche directory with registration and is paid, with PR2 would be: NRP2

Thoughts?