I might recommend Derek Allen's CCCBM. Volume 3, Bronze Coins of Gaul edited by Melinda Mays. All three volumes are basic reference works for Celtic coinage. https://searchworks.stanford.edu/view/10781819
The pic is not very good but I did some magic... I think that the coins inside the green circles are not potins but gaulish, so don´t worry, what a BIG deal, some of those potins pay the whole set! . I have some doubts with the little one in the blue circle... I'm traveling right noo , so I can´t check my (gret ) celtic library, but this paper-link may be useful for the time being: http://www.persee.fr/doc/galia_0016-4119_1995_num_52_1_3114?q=Atlas+de+monnaies+gauloises
My first feeling is not good. It seems like an extremely rare Suessions potin, "au rameau B, classe IIIa". Tooo beautiful... IMHO: fake
Ok, thank you! It was offered to me, and I turned it down because it seemed to be in too good of shape