A double mattress top is 54x75. Your size would allow a 13" drop on each side, which is enough for many people. It also allows 16" top and bottom drop, although that is deceiving since we never know if someone likes to tuck the quilt under the pillows, or has a footboard or headboard, or ???
This site quotes several "authorities" on quilt sizes -
http://equilters.com/library/quilt_i...bed_sizes.html
According to one of the "authorities", your quilt is just about right for a double bed, and according to another it is perfect for a twin. I wouldn't worry about it too much, since quilts can be used is so many different ways and there really is no standard size. If the recipient has a headboard and footboard (and if the design permits) another option is to lay it crosswise on the bed!