I found this which illustrates quite well a 'LHD' low beam pattern,
showing the raised right-hand side of the beam. If RHD units were fitted, this would cause the raised section to be on the left, dazzling oncoming motorists. As jerry mentioned, the 'slice of pie' is to block the raised section of the beam, for when those of us who sit on the correct side of the car visit the 'other' places! [
]Before I found this, I didn`t realise there was a European/N.American beam pattern, but I do recall sealed beam units on our MGB or Minis having Right Hand Drive moulded on them. If you are actually considering an amount of night driving, it would be worth upgrading your headlights, and just keep the Tripods for show!