I'm basing this on a search of honda-tech....
*edit* THIS IS A QUOTE */edit*
the type-R head should be stamped mine is stamped pr3 or 4
and the b16 is P73...
*end quote*
but frankly I think that's backwards...
heres a links someone put up...
http://www.lightningmotorsports.com/techhonacua.htm
apparently also itr heads have "green paint" on them somewhere... I think on the same side as the dist. closer to the firewall.
that's about the best I can come up with on a quick search...
good luck