Thanks for posting that Phil.
I think this is Bro. David's image showing the ejector FE latches



2nd from R is the Clam Shell used for the 1st style AE 1892-1900

1st is your round latch which I believe was used briefly in transition to the Banjo latch, but I could be wrong.
Here is another on a 2E



3rd from R the Banjo Latch used 1901-1930

4th the Rectangle Latch used 1930-1959