A modified PDP-7 under restoration in Oslo, Norway
The DECPDP-7 is a minicomputer produced by Digital Equipment Corporation. Introduced in 1965, the first to use their Flip-Chip technology, with a cost of only $72,000 USD, it was cheap but powerful. The PDP-7 was the third of Digital's 18-bit machines, with essentially the same instruction set architecture as the PDP-4 and the PDP-9. It was the first wire-wrapped PDP.
In 1969, Ken Thompson wrote the first UNIX system in assembly language on a PDP-7, then named Unics as a somewhat treacherous pun on Multics, as the operating system for Space Travel, a game which required graphics to depict the motion of the planets. A PDP-7 was also the development system used during the development of MUMPS at MGH in Boston a few years earlier.
There are a few remaining PDP-7 still in operable condition, along with one under restoration in Oslo, Norway.
http://www.soemtron.org/pdp7.html information about the PDP-7 and PDP7A including some manuals and a customer list covering 99 of the 120 systems shipped.