According to the FDIC, credit union owned Town North Bank had a tier one capital ratio of only 4.05% as of March 31, the last quarter before the bank sold its card processing division, TNB Card Services.

The bank completed a sale of TNB Card Services to Fifth Third Processing Solutions on July 6 and announced it July 7.

A spokesman for the FDIC said that while every bank's capital requirements differed according to risk, the insurer, "generally speaking" considered a bank with more than $500 million in assets to be under capitalized when it's tier one capital ratio fell to 4% or less. TNB had assets of $954 million as of March 31.

The first quarter ratio was the lowest point to which the bank's capital had fallen, according to FDIC records, but it had been on a steady slide since 2007, moving from 9.96% at the end of that year to 4.75% at the end of 2009.

The bank has declined to comment on its reasons for making the sale.