There's been some dispute on this credit until Bruno Andreacchi found Roy Thomas' letter reply, crediting Neal Adams, in X-Men #60. This tips the scale towards Neal Adams.
1. Original indexer suggested Neal Adams. Carl Gafford and Michael Evans supported Adams credit.
2. Steve Whitaker, Nick Caputo and Bob Ford disputed this and suggested Tom Palmer
Both inkers were credited with "?".
3. Bruno Andreacchi found Roy Thomas' statement of Adams inks in X-Men #60
Romita alterations on Cyclops per Nick Caputo.
Sources for letters credits are (Rosen only) The Marvel Comics Index (Olshevsky 1981); (Adams and Rosen) The Official Marvel Index to the X-Men (Olshevsky 1987), The Official Marvel Index to the X-Men (Ward 1994), and Official Index to the Marvel Universe (Vandal et al. 2009).
Miscellaneous Marvel news items.
The Mighty Marvel Checklist for titles dated June 1969.
Letters from readers - George D. Schaetzle, M. Brogdon, Michael Fortier, Kent Roberts, Greer Watson, John Monhomme and Todd Freeman, Jr.