A fortnight ago this column highlighted the problems of Protonex, an Aim-listed US fuel cell company that had introduced a two-tier quote structure to get its shares trading. US restrictions under Regulation S have prevented the shares from being settled through the Crest electronic system, leaving only the alternative of an old fashioned paper trail.

Since then xG Technology, a US communications specialist, has emerged as the only US Aim-listed company using the Swiss SIS electronic settlement system.