It's similar to the general descriptions MT uses to group TLs by:
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;"> TL General Description
0-3 pre-industrial
4-5 industrial
6-8 pre-stellar
9-A early stellar
B-D average stellar
E-G high stellar
H-L extreme stellar
M+ ???????????????</pre>[/QUOTE]