The Unicom 1620R is a 16-digit desktop display calculator from about 1971. Vacuum fluorescent tubes, AC line power, LSI chipset, percent, square root, and two memories. Badge code is often 7468-40. In the MicroBasement it sits with the Sperry 661-D and the Busicom board as the office-machine end of early LSI, not a pocket LED.
Unicom was the calculator brand of American Microsystems, Inc. (AMI). Rockwell International bought the line in 1972 and soon put its own name on similar boxes. The 1620R was built in Japan. The same chassis shows up as the Ricoh 1620R and Digitron DB1620R - typical of that OEM period.
Introduced around 1971, just as LSI replaced discrete-transistor desktops. Sixteen display digits was a selling point against 8- and 12-digit LED pockets. It is a display-only machine (the R is not a printer on this model). Production faded as cheaper handhelds and later LCD desktops took the desk.
No programming and no scientific keys beyond square root and percent. Set the decimal and rounding slides, add a tape of numbers, park totals in memory. The long VFD is the exhibit: you can read a 16-digit product without scientific notation.
The Busicom 141-PF is the printing / 4004 story. The Sperry 661-D is the pocket LED. The Unicom 1620R is the AC desk machine that still thought sixteen glowing digits belonged in an office. Same decade, three form factors.