Rolex has produced only two different models of moonphase wristwatches, references 8171 and 6062. Both models are automatic, however reference 8171 has a snap on back, while reference 6062 (see lot 350 in this sale), the Oyster version, has a water-resistant-type screw back.
Reference 8171 was made in a small series between 1949 and 1952, mostly in yellow gold. Examples in stainless steel and pink gold (see lot 349 in this sale) are very rare.
The present watch is in outstanding and original condition. The serial numbers and Rolex crown engraved to the back are still clearly visible.