2007 invitation came in a squared cover (the scan is partial, the square is too large) and franked with a meter machine. Rate seems to be the "postimpact standard distri", one of La Poste's rates for great number sent of identical commercial mail. Individually, this one cost 0,56 € per cover 50 to 75 grams weight, if 400 units were sent locally (Paris region) or 1000 units if sent nationwide.
I receive this invitation yearly, but this one caught my eye by the IGN's stamp :
"I. G. N. / BUREAU DU COURRIER / SAINT-MANDÉ"
Saint-Mandé is the town where IGN headquarters are located. Vincennes, the post office, is its neighbour.
I concluded that IGN may fear that its mail was seen as spam mail and finished directly to the trash bin. That fear may appear late 2006 or early 2007 when constumers complained that they did not receive the invite while they trash it.
IGN could order a new illustrated meter like the ones I regularly present here.