Unlike the Book of Mormon (golden plates taken away), the Book of Abraham papyri CAN be tested — this is unique

Mike draws a contrast with the Book of Mormon: those were supposedly translated from golden plates that were taken back (by Moroni) so no one can ever compare Smith's translation against the original. The Book of Abraham is different — the original source documents survive and can be compared against Smith's translation. This makes it a uniquely powerful test: if Smith accurately translated the papyri, it would be miraculous evidence for his prophetic gift; if he got it wrong, it would be decisive proof he was a fraud.