Umm, because I saw them every day, for several years? :-) (They were scattered all over the 9th floor at Tech Sq.) Admittedly, it's hard to tell a picture (from the front, where one can only see a giant wire-wrapped assembly) of the CONS machine from a picture of a CADR, but that one also has the CADR header-plate. Fair enough! And muchas gracias to Al as well for his response! Also, from a previous message: There were no CADR prototypes, other than the CONS. The first CADR built was, I am fairly certain, put into service as a general user machine; it likely had fixes applied during the bring-up process that were built in from the start on later machines, so they were all identical (i.e. no special software for that one machine), but there was no 'prototype CADR' left lying around gathering dust, unused. Thank you! I'm basing my observations from ploughing through the CADR source code, schematics and old incomplete mailing list archive.