Found a few links that you might find useful, the last link has a lot of info regarding a 20 centimes note (pasted at the bottom, as it's an old ebay item):
http://www.catawiki.com/catalog/banknotes/series/noodgeld/3431645-france-un-franc-emprunt-garanti-1915
http://www.ebay.com/itm/France-1-Franc-1915-in-VF-CRISP-Banknote-EMPRUNT-GARANTI-/281225419126
http://www.delcampe.net/page/item/id,77296464,var,MONNAIE-BILLET-BON-COMMUNAL-EMPRUNT-GARANTI-70-COMMUNES-80-62-59-1-FRANC-71553-SOMME-PAS-DE-CALAIS-NORD,language,F.html
http://www.ebay.ie/itm/FRANCE-20-Centimes-Note-Emprunt-Garanti-APRIL-1915-Scarce-LOOK-/380847605986
"FRANCE - OLD WORLD WAR ONE ERA BANKNOTE - Emprunt Garanti - Guaranteed Loan Note, 20 Centimes 1915 Issue - Small size note in Circulated Condition.
RARE EMERGENCY ISSUE FRENCH NOTE FROM WW1.
Guaranteed Loan Note - 20 Centimes denomination - Uniface
Issued for use in 70 Communes.
Printed in Blue with Watermark on white paper. There is a Black Hand Stamp on the face at the lower left.
Deliberation Du 23 Avril 1915
Series 1B. N°. 18716
2ième Emission - 2nd Issue - 5 Signatures On The Face.
Note is nicely but simply designed in Blue on White paper.
The note has two strong folds, much creasing and some surface dirt and an edge tear at the top left corner. See both scans .
Billets de Nécessite and other Emergency notes were issued in Europe - predominantly in France, during and after World War One from about 1914 and up to the early 1920's, they were used in towns and regions in place of coins which during wartime became scarce as the metal was needed for industry, their use buy and large became redundant by the mid 1920's as the economies began to recover following the privations of Wartime. On most of them there was an issue date with details of the date and time they could be re exchanged for regular currency issued by the Banque de France or other Central Bank.
There are hundreds of different types, they were issued mainly in denominations of 50c, 1 Franc and 2 Francs. They are interesting historic documents."
http://www.facebook.com/NumismaticsUK
I'm not an expert in any kind of coins, but I reckon I'm good at research and will do my best to help. Feel free to tell me my identifications/valuations/gradings are wrong. It's the only way I'll learn.