647

The Tektronix 647 is a 100MHz scope that is designed to operate in a wide range of temperatures. It takes two plug-ins, one for vertical, one for horizontal/sweep. It uses 10-series and 11-series plug-ins. Is it the only scope to use those? It is unusual to see only one scope in what appears to be the beginning of a series. Was it discontinued because of lack of demand? What replaced it?