Verizon is a CDMA carrier. And their palm phone (I think it's 650 and
700) will not work in the UK. Now, cingular also has the same palm and
cingular is a GSM network. Could it be that the phone was actually a
cingular phone. Also, Verizon has a couple of CDMA/GSM samsung phones
in their lineup. These phones have only the 900/1800 GSM bands. And are
locked AFAIK.

So, I am 100% sure that treo could not have been used on verizon and
also used in the UK. Looks like there is some missing information
somewhere.

Treo 600 GSM (cingular/Tmobile):
http://www.amazon.com/Palm-Treo-600-.../dp/B0002BRJAG

Treo 600 CDMA (Verizon):
http://www.amazon.com/palmOne-600-Ph.../dp/B000659KW8