My understanding is that the Beit Din in RSA only started keeping records in 1924.

This according to a doctoral thesis I found online some while back - "Conversion to Judaism in South Africa", by Rabbi Pinchas Zekry. It's a massive document (300+ pages) covering a lot of detail. If you can track down the author, he might be able to point you to where the archives are, since he appears to have consulted them in 1998!

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Jeremy Lichtman
Toronto, Canada