This particular shape is referred to as either 'olive' or 'spindle', and is first seen in porcelain vases of Yongzheng date.
Two similar Qianlong-marked glass vases have been published. One in the Andrew K.F. Lee Collection, is illustrated by Humphrey Hui and Peter Lam in Elegance and Radiance: Grandeur in Qing Glass, The Art Museum, The Chinese University of Hong Kong, 2000, pp. 170-71, no. 48; the other is illustrated by Zhang Rong in Luster of Autumn Water: Glass of the Imperial Workshop, Beijing, 2005, pp. 154-55, no. 24.