For a bowl of the same form, size and very similar decoration in the Victoria and Albert Museum, see Bernard Rackham, Catalogue of Italian Maiolica (London, 1940), Vol. II., pl. 141, no. 876. The central scene on the interior of the V&A bowl showing Caesar seated on a throne on a raised dais is derived from a drawing by or after Federico Zuccaro, published by Timothy Clifford in his article 'Some unpublished drawings for maiolica and Federigo Zuccaro's role in the Spanish Service' in Italian Renaissance Pottery, Papers written in association with a colloquium at the British Museum (London, 1991), p. 174, fig. 7. For a fluted ewer decorated with grotteschi divided by similar channelled edges, see Rackham, ibid., pl. 142, no. 879.
The origin of the central scene on the interior of this bowl is currently unknown, but the grotteschi decoration appears, in part, to have been derived from the designs in Jacques Androuet I Ducerceau's Petites Grotesques (Paris, 1562). See pp. 11 and 12 of this catalogue for Ducerceau engravings showing very similar grotesques. For other important Urbino pieces of this period decorated with grotteschi after Ducerceau's designs, see Christopher Poke, 'Jacques Androuet I Ducerceau's "Petites Grotesques" as a source for Urbino maiolica decoration' Burlington Magazine, June 2001, No. 1179, pp. 332-344.
The underside of this bowl is illustrated at the end of the catalogue.