Simplex retrofriction are the best DT shifters of all time, I still use them on two bikes. Mind you, I am so fucking old that using them is instinctive.
I have used Simplex Retrofriction levers and they were the best friction levers I ever tried but although I wish to stick with DT (if I go that route)...I am not sure whether you can use them with 10 speed.
Simplex retrofriction are excellent....until the 'friction' went. The trick was to run an elastic band (through the loop in the lever) to the bottle cage on the downtube!
Simplex retrofriction are the best DT shifters of all time, I still use them on two bikes. Mind you, I am so fucking old that using them is instinctive.