Latest Mobile Silk 56 user agents:

User Agent Platform Device
Mozilla/5.0 (Linux; Android 5.1.1; KFTBWI Build/LVY48F) AppleWebKit/537.36 (KHTML, like Gecko) Silk/56.2.4 like Chrome/56.0.2924.87 Safari/537.36 Fire OS 5 Fire HD 10
Mozilla/5.0 (Linux; Android 5.1.1; KFFOWI Build/LVY48F) AppleWebKit/537.36 (KHTML, like Gecko) Silk/56.2.4 like Chrome/56.0.2924.87 Safari/537.36 Fire OS 5 Fire 7"
Mozilla/5.0 (Linux; Android 5.1.1; KFASWI Build/LVY48F) AppleWebKit/537.36 (KHTML, like Gecko) Silk/56.2.4 like Chrome/56.0.2924.87 Safari/537.36 Fire OS 5 Fire HD 7
Mozilla/5.0 (Linux; Android 4.0.3; KFTT Build/IML74K) AppleWebKit/537.36 (KHTML, like Gecko) Silk/56.2.4 like Chrome/56.0.2924.87 Safari/537.36 Fire OS 3 Kindle Fire HD
Mozilla/5.0 (Linux; Android 4.0.3; KFOT Build/IML74K) AppleWebKit/537.36 (KHTML, like Gecko) Silk/56.2.4 like Chrome/56.0.2924.87 Safari/537.36 Fire OS 3 Kindle Fire