That's another mistake in McConnell - the vases shown in that colourful grouping on pg. 147 are all actually by Kastrup, dating 1960-65. The designer of them seems to have been forgotten - I've never seen them reliably sourced to JE Bang, or anyone else.
According to his work-book, Lütken first started experimenting with the Næbvase form in July '49, and kept playing with the form until July '51, when it settled into the shape that was put into mass-production. Like so:
Næbvase (http://s18.photobucket.com/albums/b108/pinkspoons/?action=view¤t=beak.jpg)
Although the Kastrup vases have a different shape when put next to the Holmegaard production Næbvaser, they do correspond to shapes also in Lütken's work-books. There are also Kastrup vases with coloured patterns within the glass, this too seems to have been a Lütken design from 1954 (as a limited edition, or maybe as an exhibition piece) where there's a standard shape Næbvase in clear glass with a spiral of violet colour running around the body.
So it seems that the Kastrup vases are an adaptation of Lütken's designs. The Holmegaard ones were only mass-produced in Akvablå, Smoke and light green, and were always fully signed (unless they're a production second). The Kastrup ones are generally colourful, and always unsigned.
I don't think that Kastrup ever signed their glass - I've not seen any, certainly.