ਕ਼

I only knew about ਸ਼ ਖ਼ ਗ਼ ਜ਼ ਫ਼ ਲ਼ (the 6 pair bindis).However, I was doing some research and found ਕ਼ It appears to be used tomake a "q" sound like in "queen". Does anyone know if this is a valid letter of Gurmukhi. Maybe it was a letter that was added, but never made it to the standardized...