A 15-second internet search turned this up .........
In answer to Andy's question ....
NSN's run from 8415-99-132-3951 NATO Size 5060/8590 to fit height 150 - 160cm and chest 82 - 88cm (the old Size 01) through to NSN 8415-99-132-3963 NATO Size 8090/1520 to fit height 180 - 190cm and chest 114 to 120cm (the old Size 9). There is an additional "Special" size listed with NSN 8415-99-132-3964......this suggests a size range from "04" through to "9" (plus "special")......."
That's the best i can do for now.
Edited to add:
Here's an NSN part finder site.
alas, it says you have a poncho so it can't be all perfect !
When i try the NSN for my smock above, it doesn't give me an answer ! Maybe because of the 'secret squirrel' nature of the kit ?