The case reference and movement are fairly common - it is the dial that makes it "rare." Even expertly refinished the watch won't command anywhere close to the value of the same watch with the original dial - such is the fate of watches like these where probably 75% of the value lies with the dial being original, in nice shape and not refinished.
And while it is not easy to find - ask
dsio - he found 3 of the 4 gold piepan seamaster calendar variants in the past 1-2 years or so all of them with original dials and in nice shape.
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