A check mark - a V shape where the right diagonal line is extended.
It is a simple representation of the visual check mark symbol. The only improvements over time were changes in thickness for durability.
This shape is often used on ovens where additional settings are accessed. The text label for these controls is appropriately 'Settings.' Visual interfaces almost always use a gear symbol for settings. The gear does not translate well to a tactile symbol because it can be confused with the cold icon (snowflake) and I think the snowflake is a stronger representative tactile icon. Two other reasons to use check mark for the settings icon
A check mark often represents a selection. This provides a logical explanation.
The check mark is a fairly easy tactile icon to identify. This provides a tactile explanation.