I may have found the origin of Sumo II. There were few cartridge makers back then and probably fewer in Japan so I had to scour through little information in their country. Both it and the Goldbug Medusa cartridges share a unique bottom shape. Medusa points to references of them being sold as the short-lived McIntosh MC 1000 & MC 800 cartridges. $1000 back then would be $2,100US today.
With the wood case the Medusa is known as the Goldbug Brier.
Mid to high end MC carts made in Japan in the 70's and 80's, the models were Brier, so named because it was fitted into a hand made brier wood enclosure (actually carved by the wife of the company's president), and the Goldbug, Medusa and Clement. All of these had the same coil arrangement but different housing and styli. The Brier was something of a legend and became the inspiration for later Koetsu and Grado models. The company also made the McIntosh cartridges that were available between 80's, those models were broadly similar to the Brier but had plastic housings.
I became involved with evaluating these cartridges at McIntosh, and even making recommendations for a few changes. In 1984 the Mark Corporation produced two cartridges for McIntosh, the MCC800 and the MCC1000. Unlike many moving coil cartridges, these did not have a peak in the response at the high end that normally emphasized intermodulation products. The brier housing was not used for the McIntosh cartridges in order to reduce mass. The coils were wound directly on the stylus cantilever. Consequently, the styli were not user-replaceable. The cartridge had to be returned to the factory for replacement and correct alignment. At this time CD's were gaining more in sales. The cartridges were available for only a short time and very few were sold. The company, Mark Corporation, has since gone out of business.