The Elder Scrolls V Skyrim Special Edition V1.5.97.0 Page

As part of the Special Edition, version 1.5.97.0 includes several engine-level upgrades over the original 2011 "Oldrim": The Elder Scrolls V: Skyrim Special Edition on Steam

While the SKSE team eventually updated for V1.6, V1.5.97.0 remains the last "pure" version of Special Edition before the engine shift. The Elder Scrolls V Skyrim Special Edition V1.5.97.0

Elder Scrolls V: Skyrim Special Edition (SSE) version 1.5.97.0 As part of the Special Edition, version 1