Inquiring minds want to know.
Your unrelenting search for knowledge befits your position as Grand Poobah of The United Kingdom of Great Britain and Northern Ireland.
This insatiable desire for knowledge also benefits, and honors, The Cult of The Zong.
I have my spare thermostat housing before me as I type. It is divided into two parts, and is held together with two 5 mm bolts which have 8 mm hexagonal heads. Each part of the housing has the word 'Skill' cast in the metal. Indeed, there
is a spring-loaded thermostat located inside the housing.
The thermostat could be replaced by separating the two parts of the housing.
The engine temperature sensor for Delphi EFI, with the blue, 2-pin connector, has the following writing inscribed upon it.
Skill
SK04052
131201
The dashboard, engine temperature sensor, with the black wire, has the following writing inscribed upon it.
Skill
130502
I suppect both 13**** numbers indicate the date of manufacture.