HP 21MX 16 bit minicomputer from early seventies. Includes a HP7900 which has a removable platter and a fixed platter. It is able to run a realtime operating system called RTE. This machine is a 2108 (without the A).
In the IO card cage there are from bottom to top; TIME BASE GENERATOR, two CRT INTERFACES, two 8 BIT DUP REGISTERS for paper tape punch and paper tape reader. LINE printer and then two cards for the disc interface to the HP7900A drive.