I have one. Nikko Shadow Trap. They were made by Kodensha of Japan. They are 101`s with a different name. Mine was made in 1971 and imported by Tradewinds of Tacoma Washington. Quite a history to them.
Golden Eagles were made by Nikko Limited in Tochigi Japan and were trade names used by Kodensha Co Ltd also of Tochigi who also produced Winchesters model 101 O/U and single barrel along with model 23 SXS and some other models. Niko also manufactured a slew of private label and standard branded shotguns and rifles for global customers, all rated above par in quality. The wide rib was pioneered by Winchesters FN produced "Broadway" which had a period of success causing a number of shotgun manufacturers to copy this feature.
Kodensha had a very jaded history eventually disappearing off the face of the earth. A Japanese friend claimed the Japanese mob was involved
I think that Miroku was a manufacture of some of these shotguns.A lot of Browning shotguns are from Miroku.They are a excellent gun maker.The BT 99 from Olin in Japan were a great single barrel shotgun that was a revolution to the single barrel trap gun.A poor mans 4 E Ithaca.Most of the Japaneese shotguns were good quality.
I have several Nikko 5000's or Nikko Golden Eagles. The one in the picture is a Shadow model, it is an earlier and rougher version of the 5000's or the Golden Eagles. It does have a rib that is about an inch wide. Nikko 5000's and Golden Eagles (and a few other variations) were similar to the Winchester 101 pigeon grades but very few parts will actually interchange. They were made in the same factory as the Winchesters. I am not sure if the Shadow version was made in that factory or somewhere else at an earlier time.
The BT-99 did not come from Olin Kodensha. The forerunner of the BT-99 was developed by BC Miroku for Charles Daly and I think there were two different models made a first and second generation. I have one of the later renditions, very few were produced before Browning took over Daly's production making a few minor changes naming it the BT-99