According to the Great Glass;
"Established 1982 by John Ditchfield, after serving a 7-year apprenticeship at Venetian Glass Co, under Franco Toffio, a skilled Murano glassblower. Hand-blown one-off vases, lamp-bases, vessels & paperweights, mainly with iridescent finishes. His signature used on its own for a couple of years before he created Glasform. "
That's why I wonder if this is an early piece before he created Glasform, as others I have seen have had Glasform as well as his signature engraved on the bottoms.