There is a procedure for setting TDC and locking it without locking the cams. I'll give you a laugh on the 95 E300 the way you find TDC is as follows some kid must have come up with it. There is a jig you fit a spring loaded device that sits in the jig that falls into a TDC slot on the vibration damper when the dial indicator placed on the cam lobe hits zero whomever designed it did place the dial indicator on the inlet cam. The TDC procedure is not in the manual but there is a procedure for finding TDC.
It's probably a two hour plus job you have to remove the intake manifold and the cam cover and everything needed to remove it. The cam lobe I am sure it is not even at its apex at TDC so the dial indicator would be past zero. I do not remember if it calls for the dial indicator to be at zero or another reading. There is also another set of timing marks apart from the slot. There is a hole in the cam sprocket that you place a pin in to check the chain stretch or time the cams and there is no punch mark for TDC like is on the older diesels. The procedure is absolutely ridiculous as is the documentation for the 606.910.
The TDC would be locked by the jig with the spring loaded tool. I'll try and find the procedure again it is not in the FSM, if successful I'll post it even though it is ludicrous in my opinion. Perhaps an Mercedes engineer got upset with Mercedes mechanics and got even with all of them everywhere.