Noriko Miwa Nov 3, 2008:

I agree with your comment. Yonyon san, thank you very much for a good explanation. I totally agree with your comment. As banks never lose money from the transactions with customers, so I think サ should be サービス, too.

952313 (X) Nov 2, 2008:

サ in katakana could be サービス When you say there is a market premium, what do you mean? Banks never lose when they provide retail FX services, so their premium is not market-driven, it's pre-determined, such as 1% for international transfer, 2% for credit card transactions, 3% for cheque, etc. Do you think they are talking about these pre-determined service charge % for FX transactions? Or do you think they are talking about profit/loss as a result of FX rate fluctuation? If it is the latter, the Japanese word would be 差益・差損 and I don't think a Japanese document would use サ to mean 差。　As Noriko's answer suggested, I am inclined to think サ in katakana stands for サービス。　In that case 外サ could be FX service fees, FX service types, or FX service something. But your explanation looks more like it is about 差益・差損 from FX market rates.　I wanted to put this in the request for clarification field but there was not enough space.