Gmeinder diesel tractors. Originally built for Munich U-bahn in 1968, purchased by Furrer & Frey circa 1998 and converted from std gauge to metre gauge to be used on construction work of the Vereina tunnel.
In 2023 both loco’s were in use on the new Albula tunnel construction work.
Loco’s appear to have been classified “Tm” previously, but were marked “Tmf” when photographed in 2023 (“f” indicates remote control)