Ascension SGZ39 GB KGV 1/2d x 2 Control Singles Cover

1915 (18 JA) Davies cover to England franked by 1912-22 GB 1/2d green x 2 both matching lower marginal with control C13 tied by individual strikes of type Z2 ASCENSION cds (23mm code B) with further strike alongside. Slight cover creasing and trivial perf tones but a very unusual usage. Original Purchased from Stanley Gibbons (Still on their card)