They were based on a Saxon VI K prototype that already ran on Württemberg's 750mm routes and replaced some ancient Klose locomotives that worked the metre gauge route between Altensteig and Nagold.
The DRG Class 99.17, formerly the Württemberg Ts 4 of the Royal Württemberg State Railways were German narrow gauge steam locomotives bought for working the 15.11 kilometre long route between the towns of Altensteig and Nagold.
The Altensteig mid-air collision was on the 11 August 1955 when two United States Air Force Fairchild C-119G Flying Boxcars collided and crashed three miles from Altensteig in West Germany.