Archival searches for optical counterparts to gamma ray bursters

The results of searches of about 1500 h of archival astronomical plates, taken with a variety of instruments at two observatories are reported. The areas of the sky photographed coincided with the positions of ten recently observed gamma ray bursts. The limiting magnitudes of the plates would in most cases have allowed the detection of the type of optical transients recently observed to be associated with gamma-bursters, although no such transients were found. A simple statistical argument is presented which allows confidence limits to be set for the repetition rates of bursters using these or other archival data.