Apologies for asking two newbie questions:

1. In the early 911 world does "matching numbers" generally refer to just the engine and chassis, or to the transmission as well? That is, is there a way to prove that a car comes with the exact transmission it left the factory with?

2. How do sellers/buyers normally prove that a car has matching numbers? I assume that if the original sales invoice isn't available (or doesn't show the engine number) then a buyer require a Porsche certificate of authenticity or would have to approach Porsche directly and ask them to confirm the right numbers?

Thanks!
Nick