The style of inscriptions on cases for the Japanese orders could be useful (assuming that the set is authentic) for their dating.
The easiest way to date cases for the Rising Sun and Sacred Treasure orders is by the form of the first /top/ kanji on the case lid.
Rising Sun and Sacred Treasure...
dating japaneseorder
dating japaneseorders
howtodatejapanese medal
howtodatejapanese medal casehowtodatejapaneseordercasejapanesecase inscription style
japanesecase kanji inscription gold
japanesecase kanji inscription silver
japanesecase kanji inscription style
japanesecaseorderjapaneseorder
styles of inscriptions on japaneseordercases