On the round 114/115 vdo kienzle clock, the adjustment knob is under that red piece of tape in Jub's photo. If you are losing 4 minutes every week, that will be a very small adjustment. I am having trouble getting mine adjusted to be accurate within a minute per day. So 4 min per week will take a lot of trial and error to improve upon.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).

Wow, cool....thanks shortsguy1 thanks marrs!

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Current:
1971 Mercedes Benz 250 (Euro Spec)
1972 Mercedes Benz 250 (US Spec)
Past:
1972 Mercedes Benz 280

Just to close this thread out:
Playing around with the clock off the parts car gave me the confidence to try to fix the clock in the 220d that I inherited from my dad. I am trying to keep the original parts to the car when possible. Anyway, following the process described in the link I put in post 5 of this thread, I put a diode and capacitor into the circuit. I cleaned the contacts. And then washed and lubed the clock. Now I will let it run a few days to adjust it to read the correct time. But it is really quite simple to do this clock repair once you have done it before. Anyway, thanks everyone for all your suggestions. I am excited to have an actual functioning clock and for it to be the same one that came with the car 45 years ago. I will have lost one of key excuses for being late. Oh well.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).