These drawings are comparable with one by Galli Bibiena from the Houthakker Collection, P. Fuhring, Design into Art, Drawings for Architecture and Ornament The Lodewijk Houthakker Collection, London, 1989, no. 877, illustrated.
Similar drawings by Giuseppe Galli Bibiena were sold at Christie's, 5 July 1988, lot 20 and 10 January 1990, lot 90, illustrated. The latter was a design for an opera performed in Vienna in 1744.