Samsung has been almost the only fan of the clamshell phones. They have a continuing line Galaxy folder, W series. Recently, there have been more news of sucessor to the G9098 and G9198, logically named the G9298 and rumoured to be W2018.(successor to W2017)
The model has showed up on TENAA, as well as >the FCC and the Wi-Fi Alliance and now even the Official user manual is also now up on Samsung's Chinese website.
The series has climbed up spec tables since starting from Folder, now quite safely positioned as a mid to mid high phone. Amongest the host of features mentioned - S Voice, Samsung Health, Samsung Pay, wireless charging, and NFC. As per previous releases, the phone will likely be limited to China only.
The W2018 clamshell features two Super AMOLED screens - 4.2” 1080p each. It has a Snapdragon 821AB chipset, 4GB of RAM and 64GB storage, all bundled up in a fairly thick 15.9mm and 234g package. The camera department is covered by a 12MP main shooter (1080p video) plus a 5MP selfie cam. Battery stays at just 2,300mAh (same as the W2017).