Proof of originality of a concept
When 2 or more inventors claim to be the original inventor of something the US Patent law must investigate to determine which is truly the original and thus eligible for the patent. It must be determined who first had the conception complete enough to apply it to practice and this is done by applying what is called reduction to practice of an invention. Conception is the "formation in the mind of the inventor, of a definite and permanent idea of the complete and operative invention, as it is hereafter to be applied in practice." A working model is very good proof. Other evidence will also be considered like original dated research and development documentation, so long as it can be proved that the date on the documentation can be verified.