[gembud] Sfstns.tbl question

I have been Googling, without success, to see whether I could discover
how the six-digit stations IDs in sfstns.tbl are chosen.  Clearly, they
are five-digit WMO station index numbers with a sixth digit added. Does
anybody on this list know how the sixth digit is determined?

Thank you.

Paul H. Harder II, Ph.D., AMS
Meteorologist and Software Developer
Weather Insight, L.P.
Direct: 713-361-4966, Tech Support: 713-361-4985
Weather Insight - Redefining Weather Risk Management

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