A Janesville company that has lettered thousands of shirts and decked out thousands of letter jackets for more than a half-century is changing hands.

Verona-based marketing company Roundhouse Marketing Services announced that it has acquired family-owned Throndsen Lettering.

Roundhouse President and CFO Tim Cullen, a Janesville resident, said Roundhouse plans to keep Throndsen’s operations in Janesville but aims to “double” the volume of embroidering and screen printing that Throndsen has done.

Throndsen has run screen-printing, embroidering and letter jacket lettering operations since 1963. It has a production facility and shop at 4375 Milton Ave. on Janesville’s northeast side.

Roundhouse closed on Throndsen Lettering last week. Cullen said owner Paul Throndsen, who has run the business since he took it over about 30 years ago, plans to retire.

Throndsen declined to comment on the acquisition Monday, referring a reporter to Roundhouse.

Roundhouse is a marketing firm that offers direct mail and email marketing services. The company has used outside contractors to handle printed or embroidered apparel for its clients, so the addition of Throndsen Lettering will broaden its range of in-house services, Cullen said.

Going forward, Roundhouse will target mainly corporate embroidering and screen-printing business, he said.

Cullen said Throndsen’s well-known letter jacket and chenille lettering business was not part of Roundhouse’s purchase.

“The letter jacket line doesn’t fit with our marketing services,” he said.

The letter jacket business will continue to operate in Janesville “until further notice,” pending a transition to new ownership, Cullen said.

Under the acquisition, Throndsen Lettering can retain its company name for up to a year. Cullen said Roundhouse eventually could rename the business.