VINTAGE ‘73 Early Minimoog Model D SN 6642

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via this eBay listing

"***Original vintage Moog, Mini Moog, Model D*** Serial #6642 manufactured by Moog Music, Inc. in Williamsville, New York, dating to approximately 1973 or 74 This is an original 1970s Model D—not a reissue—and a genuine piece of analog history! ***It needs a full service & restoration*** These early ones with the “good” oscillators are quite sought after..."

Note the listing mentions it has the first oscillators for the Minimoog, but I beleive these are Rev2 based on the serial number and date. A quick search on Minimoog Oscillator Revisions online brings up the following:

The Three Main Revisions

Revision 1
(Early Discrete) 1970 – 1971
(Serial #1001 to ~1210) 100% discrete design featuring no operational amplifiers (op-amps). Utilizes a single temperature-compensated resistor ("tempco") shared globally across all three oscillators. Known for a raw, unpredictable, and remarkably "beefy" character. However, it suffers from notorious environmental drift, scaling issues, and poor tuning stability.

Revision 2
(The "Old" Board) 1972 – ~1979
(Serial ~1211 to #10174) Transitioned to utilizing early Integrated Circuits (ICs) while preserving discrete transistor sub-circuits. Features 7 calibration trim holes exposed on the rear panel. This is the most common version found in vintage units. It introduced individual scaling adjustments per oscillator. It successfully retains the classic organic texture and phasing behavior while improving baseline reliability.

Revision 3
(The "New" Board) ~1979 – 1981
(Serial #10175 to end) Completely redesigned to use modern, highly accurate uA726 heated differential pairs (or specialized tempco configurations) for exceptional tracking stability. Features 17 trim holes on the back panel for ultra-precise high-frequency calibration. Delivers rock-solid tuning stability. Purists sometimes debate that its tighter tolerances alter the classic oscillator-phasing behavior, making it sound slightly cleaner or "thinner" compared to its older siblings—though it remains vastly thicker than most standard analogs.

So this one appears to be a REV 2.