In starting this research I looked at my hammer guns and found 3 that have this oversize top lever and they range in years from 1910-1918. One is a 16 gauge from 1910. The early Syracuse hammer guns that I have and seen do not have these oversized top levers.
In correspondence with Mike Harris, he doesn't have or and he doesn't believe he ever has seen any. Once you see one you won't forget it because it is straight tapered whereas the narrow one has a cut-out of both sides.
If anyone has one could you send me an email with the serial number, barrel length, gauge as I would appreciate it for my records.