Gosh, I haven't heard the term Regulo for years. I think my mother used it, so I assume that Regulo and Mark are the same thing.
It's part of the lexicon of our kitchen!
When my parents moved in with us in 2001 - a few months before my mother's 90th birthday - they were Determined To Make Themselves Useful Around The House. Thus it was that my mother cleaned the cooker so vigorously that she sandpapered all the numbers of the regulo knob and then felt so guilty that she bought us a new cooker.
It was as a pre-emptive measure that we bought our first dishwasher, shortly before they moved in. I knew that they would want to "help" with the washing up, and we also knew what their dishwashing quality control was like, and how it left a good deal to be desired.