Well the one engraver that I can name for sure is Albert E. Spangler who appears to have started working for Lefever in 1887 at the Syracuse plant.
Elliot briefly mentions Jacob Glahn and possibly his sons; A.E. Spangler and perhaps his brother Wilton; L. Delunsch; R.A. Arthur; possibly Frank Mason and sons Roy and Max; and R. Kornbrath. The Syracuse city directory shows at least 20 engravers, circa 1888. There were a number of gun makers in operation there as well other businesses that would have employed engravers. How many DM Lefever employed at any one time is unclear.
Elliot talks about every other feature of the Lefever guns and never mentions the step, at least that I can find. The earliest photo of a step is a Nichols & Lefever hammer gun. The partnership lasted from 1876-79. The lowest grade there is a photo of with the step is a C grade.
Also, the radius seems to change without rhyme or reason. I prefer the radius of the "acorn gun" as well.
On some of the Optimus guns, there is a circular horn insert with an ivory pin in the middle. Elliot states that was an attempt to prevent the wood from cracking as it did on the LC Smith's. Whether he has documentation for that or it is his opinion is unclear.
Pete