Hello, my dear Friends,
Thanks to Zac UK to poin me on this topic.
well, this is not mintmark - as we know Mint of Pretoria has mintmark SA.
This a stylized abbreviation of engraver, - Armand Bonnetain ( AB), and it is presents on all coins with elefant - 1,2,5, 50 francs.
Also, on hexagonal 2 franc coin, which was struck in Philadelphia , and not in Pretoria.
There are no coins with/ without this markl, - it is just someties visible clearly, or visible less. For example - this coin from ebay, which is not so worn, but engravers initials almst invisible, although YOu can see a small part of it.
I believe we had a discussion about this mark, and as I remember, I was the author of the topic, but probably i was in other forum..
Anyway, - it is engravers initials. and I will add description in our cat.
Thank You for Your attention, dear colleagues.
Yours
david