Ah thanks. It's one of those warm browns that always seem to appeal to me. I thought it may have been Pelkan Brilliant Brown.

I've been using Diamine Ancient Copper recently, which I like a lot. Upon googling comparisons of Ancient Copper to Chesterfield Antique Copper, the consensus seems to be that despite the similarity in names, they are different inks -- D. Ancient Copper having more red tones than the Chesterfield. Really lovely, but I understand Chesterfield inks are no more.