I coudn't find it in Chambers either mrcroft .Mine is ancient though .
I googled it in the end .It's a financial term ( in french)
http://www.vernimmen....lettre_de_change.html
and also means volumes of books in German.
Sorry that link was no good but this is what I found
Elle peut être écrite (papier) ou dématérialisée sur une BANDE magnétique (relevé). Equivalent anglais : Bill of exchange · Electronic bill of exchange