Quad Band White Stick Antenna

[G4RMT]

One of my suppliers asked me to try a quad band antenna - advertised as 28/50/145/430MHz - so I thought I'd give one a try and it's rather odd.

The three usual ground plane elements screw in and are a bit big and whippy, but I stuck it on the analyser and got some very strange results. The best match, frequency wise was as follows:
27.4MHz
48.2MHz
94.8MHz
144.7MHz

430MHz wasn't there at all, but there was a really nice match at 263MHz?

All in all, it has an overall frequency plot rather like a discone - no real gain, but some response everywhere - but above about 350MHz or so it's not much cop at all.

Certainly it's not going to be one I'd like to sell, but I'm tempted to look inside, destroying it.
EDIT Allen keys got it open without damage!

Here are the plots and internal pics if it helps anyone.
https://www.eastanglianradio.com/analyser/qb48.jpg
https://www.eastanglianradio.com/analyser/qb90.jpg
https://www.eastanglianradio.com/analyser/qb27.jpg
https://www.eastanglianradio.com/analyser/qb200.jpg
https://www.eastanglianradio.com/analyser/qb144.jpg
https://www.eastanglianradio.com/analyser/qb100-463.jpg
https://www.eastanglianradio.com/analyser/qb1.jpg
https://www.eastanglianradio.com/analyser/qb2.jpg
https://www.eastanglianradio.com/analyser/qb3.jpg
https://www.eastanglianradio.com/analyser/qb4.jpg