Glad I took Marshall's advice and replicated the chain stretch measurement on my '95 E300D with the OM 606.910 engine. My first measurement on Saturday was 4 deg. The subsequent measurements, today, were 3 deg, 2 deg and 2.5 deg. Think I'll keep this chain and check it again in 30 or 50k miles.
I discovered an important trick that other 606 engine owners may want to know - The cam can be indexed for #1 piston TDC by running a pin through holes that align the left cam gear and the front cam tower. One of the bolts that holds the cam cover on the head is the perfect size to use as this pin. This bolt will fit tightly enough that I estimate the bolt will only fit through both holes within < 1/2 deg of crank rotation. When looking at the engine from the front of the car, correct crank rotation is clockwise. To measure chain stretch, you must approach the index postion only from the clockwise direction. Backing the crank off a fraction of a degee reverses the play in the chain and makes the measurement meaningless. Ned Kleinhenz '95 E300D x2 '85 300D '80 300TD
