Nikko was the trade name for Olin Kodensha Co, up in Tochigi, Nikko Prefecture, Japan. Nikko was in a partnership with Winchester, and was known to have saved the best wood for its own Nikko guns. The factory burned down in the 80's and most of its records were lost. Nikko made guns for Winchester (such as the 101 I have) and also sold like guns under the Nikko name, as well as its own guns. I have a Nikko Shadow and Nikko NTG - both are lovely.
Patrick, are you sure about the factory burning down? It was certainly in business through the Parker Reproduction years, which lasted until early 1989. Also through the period during which Classic Doubles took over importation of the 101, and switched from the sxs Model 23 to the Model 201. It was my understanding that the factory either closed or was converted to other purposes.