Timex Sinclair was a joint venture between the British company Sinclair Research and Timex Corporation in an effort to gain an entry into the rapidly-growing early-1980s home computer market in the United States. The choice of partnership was natural as Timex was already the main contractor for manufacture of Sinclair's ZX81 and ZX Spectrum computers at its Scottish plant in Dundee.
It was Timex of Portugal, though, that took on the R&D and the local manufacturing of the models to be exported to the U.S. Although both Timex of Scotland and Timex of Portugal were full subsidiaries of Timex, internal rivalry, whether unintended or purported, meant there were no contacts nor experiences shared between the two plants. Timex of Portugal also sold the Timex Sinclair models in Portugal and Poland under the Timex Computer brand.
Source: Wikipedia, "Timex Sinclair", available under the CC-BY-SA License.