George N. Kates notes in Chinese Household Furniture that this lampstand probably originally held a metal sesame oil lamp or a pewter pricket candlestick (p. 121, notes to cat. no. 110).
Compare a similar pair of adjustable lampstands of slightly later date, in the collection of the Minneapolis Institute of Arts (R.D. Jacobsen, Catalogue, 1999, pp. 168-169. no. 59.), sold at Christie's, New York, Important Chinese Furniture, Formerly the Museum of Classical Chinese Furniture Collection, 19 September, 1996, lot 49.
For a discussion of adjustable lampstands, their construction and use, see Sarah Handler, "Carriers of Light: The Chinese Lampstand and Lantern," Journal of the Classical Chinese Furniture Society, Summer 1994, pp. 19-34, and her corresponding chapter in Austere Luminosity of Chinese Classical Furniture, Berkeley, 2001, ch. 18, pp. 303-318.