Distribution of high-confidence WDs (sources with Pwd > 0.5) with derived masses (assuming H atmosphere) from Gentile Fusillo et al. (2021) in the Gaia CMD. The dashed black lines are the cooling curves for 0.5 and 1.2 M_⊙ DA WDs from Bédard et al. (2020) and a 4.3 Gyr cooling age isochrone. The isolated OC WDs should all lie within the area bounded by these curves. The preliminary selection cut (dashed red line) should be flexible enough to detect these WDs even in the presence of significant uncertainties.