well i dunno about the code stamp"trustme i looked for about an hour" but the most visable thing would be the valve cover.its gonna be bright red,if you got a ctr/itr head you want people to know it so if he was to say "oh i just swapped a diff valve cover" thats bs,if its stamped pr3 its a stock b16a head and not a itr head.this i9s some little info i found about the motor.Other Specifications:
Country Specs: Japan-specifications
Engine Code: B18C-R (Japan Domestic Market)
Swapped From: JDM Honda 98-01 Integra Type-R
Produced: 1998-2001 in Japan
i would ask him what it redlines @ if he ses 8900 rpm then its an itr head.
i dont really know if this helps you or not but you have helped me a few times in the past so i thought i would try.