Mystery HP 1000 board

[Eric Smith]

On Thu, Jun 16, 2016 at 11:08 PM, tony duell <ard at p850ug1.demon.co.uk> wrote:
> Subassemblies (like PCBs) have part numbers with 2 groups of 5
> digits. The first group is the model number of the instrument that
> first used that subassembly, padded with leading zeros. So for
> example the CPU data path (ALU and registers) board in an
> HP9830 is an 09810-66514, as it was first used in the HP9810.

On some early HP gear (1960s), the subassemblies and model-specific
parts have a 4x5 or 4x4 part number, with the base model number as the
first part, rather than the later 5x5.