vintage crochet patterns

Posted by: christineka (IP Logged)
Date: April 02, 2009 10:12PM

I've run across this patter in my search for thread bonnets:

It calls for No. 100 crochet cotton and does not specify a hook size.

I can find no such thing as no. 100 crochet cotton and I have no idea which size hook to pick. Any ideas?