To all who are interested:

I did get a response from Tom Whittmann about this dagger. I sent him several pictures and a good description. He said that it is 100% authentic and the roman numeral is correct for this dagger. He said that it is one of the very first SS daggers to bear the RZM mark, and that he has one pictured on page 20 of his book. Now I don't have the damn book handy! I have to just buy one myself and quit borrowing one from a friend! Anyone have one that they want to part with? Maybe I should post in the wanted section. Otherwise I will have to just buy one off Tom's site. I still want to find a known maker piece with the same tang marking. It seems that this marking is perhaps only seen on this 188 marked dagger?? Something else out there has to have it. It looks like this might be the only hope in finding out who the maker is. I thank all of you who have offered opinions on this dagger!