iPhone 7 phones sold in Japan carry the Ministry of Internal Affairs and Communications regulatory mark engraved on the back due to the iPhone 7 FeliCa Apple Pay support. It was a bit of a brouhaha a year ago even though there was a new MIC guideline in the works to display the certification mark on the screen instead of the case.
Nice to know that is all settled, the MIC certification mark for FeliCa is on the screen now. Global FeliCa inbound iPhone 8, iPhone X and Apple Watch Series 3 devices are covered for use in Japan without having the mark engraved on the case and Japanese iPhone 8, Apple Watch Series 3 and later models dispense with the case mark as well.
Update: not all global FeliCa iPhone SKUs display the MIC screen mark, only the Japanese SKUs. Apple displays the MIC mark where it is legally required (models sold in Japan). iOS 11 updated iPhone 7 Japanese models display MIC certification both on the screen and the back case. All iPhone 8 and later Japanese SKU only display the screen mark.
Update 2: recent iOS versions now display all necessary regulatory marks grouped by region (USA, EU, Japan, etc.), i.e. everything is covered everywhere.