From introduction in 1922 --
1922 Lefever Arms Co., Inc. folder.JPG
up through the 1928 Lefever Nitro Special flyer they were shown with the half-pistol grip. Beginning with the 1929 Lefever poster the Nitro Special is shown with the capped full pistol grip. Don't have a picture of the 1929 poster on file, but here is the 1930 which adds the vent rib double trap gun --
1930 Poster.jpg
The definitive work on the Ithaca Gun Co. Lefevers is Walter Snyder's article in
The Double Gun Journal, Volume Thirty, Issue 1.
Similarly, J. Stevens Arms Co.'s low priced hammerless double their Riverside Arms Co. No. 315 had a half pistol grip from its introduction before WW-I through the 1927 catalog --
No. 315 Catalog No. 57, 1927.jpg
By the 1929 J. Stevens Arms Co. catalog they had renamed their low priced line to Springfield Arms Co. and the No. 315 had a full pistol grip.