This is a set of injection-plastic detailing parts for use with ship models.
From the manufacturer:
This set features equipments applied to Japanese warships in Meiji era, primarily around Russo-Japanese War. Applicable to the model kit or scratch build model of the same period. As detail equipment of Japanese warship in that era was mostly identical to that of British warship, you can use this set for improving detail of contemporary British warships. Especially, some of the boats can be applicable up to the WWII era.
These equipment parts are molded in light grey.