The draft 2003 edition of the Oxford English Dictionary lists the earliest known usage of the concept as being in L. Chatterton's book Modern Cookery published in 1943: "Afternoon tea scones… Time: 20 minutes. Temperature: Gas, Regulo Mark 7". This particular example also illustrates the term in combination with the word "regulo". This usage pattern is now almost obsolete, but still used by some of the older members of society.
The term "gas mark" was a subject of the joint BBC / OED TV series Balderdash & Piffle, in May 2005, which sought to establish the history of the term. The earliest printed evidence of use of "gas mark" (with no other terms between the two words) appears to date from 1958.
|225°||107°||Very Slow/Very Low|
|250°||121°||Very Slow/Very Low|
In general, the conversions between a Gas Mark temperature and a Fahrenheit temperature are given by
where kf = 275 °F.