A gold Merovingian National Series tremissis dating to c 650-70. The obverse reads ATACIACO and the reverse FRATECLISELO. The PAS record gives this as the mint of Allassac and moneyer Frategiselo.
In a quick search, I couldn’t find another example of this mint and moneyer. The best reference on Merovingian coins is still the five volume work by Belfort, published in the 1890s. That listed about 6,500 coins, many of them known from a single specimen. New coins continue to turn up in England and this could be yet another. It has been designated a Find of Note for inclusion in British Numismatic Journal ‘Coin Register’.