The report refers to "Panel Banks" by number and "Broker Firms" by letter. Each Panel Bank was a member of a British Banker's Association panel that contribute Libor submissions in one or more currencies. Libor is currently set for 10 currencies, each of which has six to 18 banks on its panel. Because we know the identities of the banks on each panel, we can narrow down the possible candidates.
(Learn More: What is Libor?)
Every instance of UBS roping another bank in on its manipulation scheme involved the setting of Libor of Japanese yen transactions. We know, therefore, that the bank was a member of the yen panel. There are 18 banks on the panel, including UBS.
We know that 17 banks are on the yen Libor panel with UBS: Bank of America; Bank of Tokyo-Mitsubishi UFJ Ltd; Barclays Bank plc; BNP Paribas; Citibank NA; Credit Agricole CIB; Credit Suisse; Deutsche Bank AG; HSBC; JP Morgan Chase; Lloyds Banking Group; Rabobank; Royal Bank of Canada; Societe Generale; Sumitomo Mitsui Banking Corporation; The Norinchukin Bank; and The Royal Bank of Scotland Group. Five of these allegedly cooperated with UBS in the manipulation.
One of those is most likely to be Barclays, which has already copped to manipulating Libor. So that leaves four out of 16, or one-quarter of the entire group. Overall, it means that one-third of the panel was engaged in corrupt activity.
The UBS trader at the center of the FSA report is known as Trader A. He is depicted as being directly involved with much of the wrong-doing or the person on whose behalf attempts to manipulate occurred. He also used to work at Citigroup, one of the possible candidates for the unnamed Panel Banks.
It seems likely that one of the broker firms is London based RP Martin. Earlier this month, two of its employees, Terry Farr and Jim Gilmour, were reportedly arrested in connection with the Libor investigation of the UK's Serious Fraud Office. (Read More: Dozens Likely Implicated in UBS Libor Deal.)
That's about as far as we can go without engaging in pure speculation.