The TEC-1C and TEC-1D were designed after the last issue of Talking Electronics was published. So no articles to show here, only a component list.
The design is identical to the TEC-1B. Only the PCB had some improvements, simple cheap tactical switches are used for example, function names are printed as part of the silkscreen on the PCB.
While the original TEC-1D is still available as a kit from Talking Electronics, a recent production run of the PCB as Reproduction 2018 is available from Ben Grimmett via ebay e.g. The latest is double sided, so no more wires!