This new style left hand (cold) stem and handle assembly with check valve and bonnet is from T&S Brass. It comes with a lever handle, spring check, blue index, and screw. Fits all T&S faucet models. T&S Brass part number 002711-40NS.
For right (hot) hand stem assembly, see #68458
EC Part Number: #68549
Manufacturer Number: 002711-40NS
Manufacturer: T&S Brass