While there is no documentation, signs point to Yasuo Imai of Seki Japan. Yasuo was an excellent Japanese knife craftsman in the 1950s and 60s. His son Seizo later joined the business.
Yasuo made many popular knives that we have come to know. Along with Seizo, Imai made manual stiletto knives for importers such as Valor and Westbury that were identified as the “bull fighter.” These knives in particular shared a lot of similarities to rizzutos. The shape of the bolsters with both squared and rounded, batwing guards, filagreed bales and metals used are very similar.
The matador/dragon manual knives of theirs are also eerily similar to the bullfighter lever lock automatics sold in Mexico. There was also an importer named Precision International which had some of their knives made in Japan. They had a line of Japanese picklock knives that were stamped Korium Pic and sometimes just PIC that were thought to have been made by the Imais. They appear very similar to rizzutos.
These were knives that were made largely to be sold in Mexico to US tourist and that is the same and obvious strategy of the rizzuto knives.
It is logical that the rizzuto estileto milano knives were designed and produced by Yasuo and Seizo Imai of Seki prefecture in Japan, but that does remain a theory.
Rizzuto with box image courtesy of Dan Woods