Most of the Wirt screw cap dropper filled pens are short, slender, or both. Only one pen pictured is a standard sized pen, while the rest are smaller in some way. These pens typically have no barrel or cap imprint at all. In my collection, one has a standard 3 line imprint, and one has an unusual imprint (the full sized pen). The rest have no imprint. Also note the shape of the section with a very short and very acute angle to the flange on the section. This shape matches the Esterbrook Relief pen that is likely a Wirt pen. Nibs can either be numbered or wreath nibs. All have a vented underfeed and a ventless nib.