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Not much I could find on the schooner CURIEUSE (most French sources give her as goélette), the vessel depict on the stamp is not schooner rigged but more like a barque.

In connection with the expedition of Marion Dufresne (1724-1772) two ships La DIGUE 360 ton, and La CURIEUSE the last was under command of Lt. Lampériere, most probably both ships were owned by the French King and managed by Compagnie des Indies.
On a voyage she landed in 1767 what is now called Curieuse Island, named after the ship, the island is one of the Seychelles group in the Indian Ocean.
There was a corvette armed with 6 – 2pdrs., tonnage 30 tons with dim. 50 x 11x 5.6ft built by Cochois, Le Havre in 1702, but I can not find a connection between this ship and the Seychelles Islands.

Seychelles 1999 R3.50 sg892, scott806.

Source: Various internet sites.

Watercraft Philately Nov.-Dec.1978 page 29 has the following article on the “First Landing on Praslin Island.

The 200th anniversary of the first landing of Europeans on Praslin Island was commemorated in 1968 with an issues of stamps by Seychelles. Praslin lies about 40 miles northeast of Mahe Island, the principal island of the Seychelles group in the Indian Ocean.
The second Seychelles Expedition, fitted out by Desroches, the Governor of Ile de France (Mauritius), and the Intendant Pierre Poivre, was led by Chevalier Marion Dufresne, who had been a captain in the defunct French East India Company with a varied and colourful career at sea. Two French naval vessels were provided, the flute La DIQUE, built in 1756, and the Goélette (schooner) La CURIEUSE, also built in 1756. The expedition sailed in December 1768 and returned in January 1769.
The purpose of this expedition was more than exploratory. The intention to exploit the timbers of the islands is substantiated by the provision of two ships, and the fact that Lieutenant de Lamperiare, commander of La CURIEUSE, was assigned a Corporal and four men to work the forest. There are many references in the journal of Dufresne to the commercial prospects of the island. Quite by accident the expedition discovered the source of the famous and highly priced nut, the “coco de mer”, (seen on the 85c stamp) https://en.wikipedia.org/wiki/Lodoicea ,which grown on Praslin Island.
As a footnote, it is interesting to know that Dufresne was massacred by natives (Maori) of New Zealand in 1772 during an exploratory voyage from Mauritius, and died under circumstance similar to those surrounding the death of Captain James Cook. http://www.shipstamps.co.uk/forum/viewt ... sne#p12165

Source: J.S. Fenemore, Ref: Guy Lionnet, The Seychelles, Musee de la Marine, Paris.
Seychelles 1968 20c/2R25 sg253/56 scott248/51. (La DIGUE is the larger vessel on the stamps.)