Thanks to some helpful folk on here, I've been able to discover more re Bellone and Sultane. It seems there are significant differences:
* They share no common syns: Bellone - Bellona; Bellonne; Ficus carica Bellona Risso.
Sultane - Sultana; Fig of Nice; Black Nice; Nice; Antibes; Grosse de Juillet; Dark Sultane; Noir de Juliet.
One modern source claims Bellone bifere as a syn. for Sultane.
*Trees/growth characteristics: Bellone - strong tree, 16 feet, drooping branches, slow growing. Mid-late variety.
Sultane - Upright with minimal suckering, fast growing. Fruits early.
* Leaves: Bellone - large, deeply 3-5 lobed.
Sultane - '..big leaves of type 3 with 5 lobes,shallow..".
*Brebas : Bellone - rare or none.
Sultane - Two crops, very productive.
*Fruit: Many similarities, but, Sultane is described as having a distinct pruinose bloom, whereas Bellone has no bloom. This distinction is clear in pics. For me, the most convincing distinction is that Bellone is easily damaged in handling and transport whereas Sultane has "skin unusually firm, resistant to injury', suggesting quite different skin textures.
As I can find no record of Sultane ever having been in Australia, I don't forsee any confusion in my qhest for our 'lost' Bellone.
Regards Geoff