> I'm trying to look into why Stanley called it a "block plane", and earlier
uses of the same term seems a useful avenue of research.

From Stanley Blood and Gore:

Stanley, in their marketing propaganda, claimed that "_A Block Plane was
first made to meet the demand for a Plane which could be easily held in
one hand while planing across the grain, particularly the ends of
boards, etc. This latter work many Carpenters call 'Blocking in', hence
the name 'Block' Plane._" 

The 9 1/2 was manufactured from 1873 to 1981.  SB&G doesn't give a hard
date for the Stanley marketing propaganda, but the article (
http://www.supertool.com/StanleyBG/stan2.htm#num9.25 ) 
implies that Stanley is responsible for the designation, "block plane." 

I've found them addictive.  No idea how many I have, only that I don't
have (yet) one of the earliest styles.  

Mike in Woodland