I emailed the seller with the question, and he kindly supplied a photo of the bottom of the toggle. I have come to expect a capital letter (a worker's mark??) to be stamped on the underside of an authentic Navy rear toggle, this one appears to be I . It is a bit difficult to tell, but one could also compare the machining characteristics of the bottom of the toggle rails.
It is worthy of note that the seller does not make the claim that this is an authentic piece.
(Top toggle is the one for sale, bottom is from my own Navy.)
--Dwight
