The two components of a quasar pair of separation 7.3 arcsec, discovered in a low-dispersion spectroscopic survey with the Canada-France-Hawaii telescope, were observed with the Multiple Mirror telescope and found to have redshifts of 2.152 and 2.147, with uncertainties of + or - 0.005. This pair, with approximate magnitudes of 19.5 and 21, is interpreted as the third known example of gravitational lensing. It is emphasized that survey techniques such as that used to discover this pair have found over 1000 quasars. The fact that pairs with smaller separations have not been found in this way is considered puzzling.
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Weedman et al. (1982) studied this question.