Hello SU1977,
I have looked on the web and on
ebay and Delcampe for a while searching for what this could be and any info on it, as I know nothing before about it.
The cancels on Delcampe lettres seem to have different dots or partial dots below the Tuamotu Islands names, and so could indicate different post offices or clerks or times even perhaps.
Under the administration of French Polynesia Tahitian Islands group at the time I think. The SCE on the postmark could mean Society or 'group of' in French.
I would think, looking only at pictures of islands there (the Muamotus) and ships passing through now, that large ships could dock or come close to some of the islands.
Wikipedia Tuamotus:
http://en.wikipedia.org/wiki/Tuamotus