I found this Seiko knife in a local antique store. I was actually hoping to find a Watchmaker model. I quickly realized that it was smaller than 84mm. I have photographed it next to a 74mm Ambassador and a 93mm Solo for comparison. The Seiko knife is in fact 74mm and was made in Japan. The interesting part, is that main blade is beveled on the backside. This allows for removal of the watch case backing without pulling the blade out. By the way, the second blade is just that, a smaller blade. Sorry for the bad cell phone pics. My PC is down.
Robert