This pen has the two line imprint and paddle overfeed. Yet it appears to have a normal slip on cone cap (not meaning taper, but meaning conical inside to seat to the conical section and barrel).
If you look more closely, it is a large straight cap. But instead of seating on the section, it seats past the section onto a straight portion of barrel. The stop serves as a stop for the cap. The posting end is straight, not tapered and the step also serves as a stop on that end. I believe that this represents a transitional cap style from the small straight cap to the traditional cone cap. The imprint date and feed seems to justify this assumption, as the pen predates the traditional friction fit cap with conical shape inside.