1600+434: a new gravitational lens system

We report the discovery of a new gravitational lens system associated with the flat-spectrum radio source 1600+434. The system has been found in a new large survey of such radio sources. It consists of a 1.4-arcsec double radio source with an associated optical double at the same position and orientation, and with an almost identical flux density ratio to that in the radio. Spectra of the light from two optical images show broad emission lines with a redshift of 1.61. The spectral data are not of sufficient quality to show that both images have identical spectra. Nevertheless, we argue that the probability that 1600+434 is indeed a lensed system is very high.