I haven't looked at that model Briggs, but most of them have a keyhole valve retainer: you just compress the spring by pushing down on the retainer (usually with your fingers) while holding the valve head to keep it from opening, then push the retainer sideways. After it moves sideways if you take the pressure off the retainer, it will just slip over the groove in the end of the valve stem and come off.
If your engine has car-style split collets retaining the valves, you will need to compress the valve spring with a spring compressor or (Joe Carroll's trick) a couple of cable ties, then push the valve head back into the closed position to free the collet from the retainer. Then you poke the sharp tip of a knife between the two halves of the collet, so they fall off the valve stem.
I've never had much success identifying whether parts are original or not. Factory purchasing departments keep changing their component sources depending on price, quality and reliability of supply. What they were buying six months ago is often no indicator of what they are buying now.
