Wie wäre es denn damit:

Serial.

Check the dial version with the serial. The usual and these are only guidelines since Rolex collecting has no hard rules.
Mark I Dial, 1.6-2.2 mil
Mark II Dial, 1.6-3.5 mil
Mark III Dial, 2.6-3.5 mil
Mark IV Dial, 3.0-5.2 mil

Its generally accepted by collectors that the DRSD were produced in the 1967-1977 range with the last batch in the 5.2 mil serials. While there might be some exception to the above, this is what is currently accepted by collectors..

(Quelle: http://www.doubleredseadweller.com/drsdcollecting.htm)

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