A 5-digit Nixie tube counter, 300 KC. Cost $1175 in 1961.
The example shown below is a Dymec version. Note that there is no branding on the front panel at all; the rear panel has a metal HP-style serial number plate, but it does not say “Hewlett-Packard”. There is a foil sticker above the serial plate saying “5512A-DY M2”. Internal parts have 1962 date codes, and have the “hp” logo.