Recently I purchased what turns out to be a 704 meter in a 704B case. I’m not sure why the meter case was replaced, but it is possible the original case sustained damage and was replaced. It is inscribed as serial number 0101. With it I purchased an original manual, 72 to 300 Ohm adapter and a sheet of paper with hand-drawn test lash-ups, presumably by the meter’s original owner. Photographs are available at The Old CATV Equipment Museum: http://theoldcatvequipmentmuseum.org/
Regards, Ned A Fenimore, Senior Technician, Clear Creek Mutual Telephone and Television in Oregon City, Oregon.