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We report on three optically bright, ~15th mag, point-sources within 10arcsec of each other that vanished within 1 hour, based on two consecutiveexposures at Palomar Observatory on 1952 July 19 (POSS I Red and Blue). Thethree point-sources have continued to be absent in telescope exposures during71 years with detection thresholds of ~21st mag. We obtained two deep exposureswith the 10.4-m Gran Telescopio Canarias on 25 and 27 April 2023 in r andg-band, both reaching magnitude 25.5 (3-sigma). The three point-sources arestill absent, implying they have dimmed by more than 10 magnitudes within anhour. When bright in 1952, the most isolated transient source has a profilenearly the same as comparison stars, implying the sources are sub-arcsec inangular size and they exhibit no elongation due to movement. This tripletransient has observed properties similar to other cases where groups oftransients ("multiple transients") have appeared and vanished in a small regionwithin a plate exposure. The explanation for these three transients and thepreviously reported cases remains unclear. Models involving background objectsthat are optically luminous for less than one hour coupled with foregroundgravitational lensing seem plausible. If so, a significant population ofmassive objects with structure serving as the lenses, to produce three images,are required to explain the hundreds of sub-hour transients.

A bright triple transient that vanished within 50 minutes