https://www.techradar.com/news/amd-radeon-rx-640-re-branding-for-polaris-gpus-hinted-in-new-drivers

While we continue to wait for AMD to push graphics processors forward with Navi and its 7-nanometer architecture, a leak is suggesting that may not be the only things AMD is preparing. A new graphics card name was discovered in AMD's Adrenalin 19.4.3 graphics drivers by a TechPowerUp reader.

The newly identified card is a Radeon RX 640. This would put it on the lower end of the performance spectrum per AMD's naming convention. But, this would also suggest it's neither a Vega nor Navi GPU.