St Vincent Stamps Easter 1974 Airmail (possibly?) to Seychelles Unsual (w).

Envelope has "VIA AIR MAIL" just visible under the bottom of the stamps. St Vincent cancel on front and Seychelles cancel on back. Not sure if this did go by plane or not. In good condition - vertical crease on left and a few bumps here and there. Nice unusual item though. Please see photos.