The Krystal Company “Krystal” on Thursday announced the sale of the 80-year-old hamburger chain to Argonne Capital Group, LLC, a private investment firm based in Atlanta, Ga., for an undisclosed amount. Krystal announced late last summer that it had retained Piper Jaffray & Co. to market the Chattanooga-based chain for a potential sale.

“Finding the right owner, one that will continue to uphold the qualities of the Krystal brand that have made it a Southern icon, has been an important part of this transition,” said Krystal President and CEO Fred Exum. “ Argonne recognizes the strength of the brand and provides a foundation for the Krystal family of employees and franchisees to continue its expansion by serving our loyal customers.”

The Krystal Company has more than 6,000 employees, and owns and franchises a total of 360 restaurants in 11 states throughout the South. The quick-serve chain opened 10 new company-owned restaurants this past year, and will continue with new store developments in 2012 and beyond. Officials also said the company’s headquarters will remain in Chattanooga.

“We have watched with great interest as Krystal has continued to develop quality products, offer outstanding customer service, and maintain brand dominance through the recession,” said Michael Klump, founder and president of Argonne.

The Argonne team sees a great opportunity with this acquisition and is excited about adding The Krystal Company to its portfolio. Krystal’s board will include Michael Klump and Karl Jaeger from Argonne who will be joined by Stockton Croft, a continued advisor to Argonne, and Harsha Agadi, former president and CEO of Church’s Chicken.

The fast food icon made famous by small burgers with a big taste craved by millions throughout the South, finished 2011 with increased sales, an increase in per-transaction sales, and consistently outperformed the overall quick-serve restaurant (QSR) sandwich category in driving traffic last year. The company continues to experience growth in 2012.

Piper Jaffray & Co. served as exclusive financial advisor to The Krystal Company in the transaction, and King & Spalding LLP served as its legal counsel.