Well first off ignorance is the common denominator when dealing with people. Secondly, this is a capitalistic soceity and you get what you pay for and by the looks of the pictures a pretty good deal. Third, he needs to google it instead of hassle you. Finally, all as is purchases are final and this is now his problem.
I hate to sound harsh but you have gone about and beyond your obligations as a seller and nothing more should be asked of you. He needs to take the CRT.5 and his attitude elsewhere, maybe an LHS?