Hedge fund firm MMI Investments is continuing to push for The Brinks Co. to break itself up.

In a letter to the company’s board on Wednesday, MMI’s Clay Lifflander compared Brinks with fellow conglomerate Tyco, which recently completed a long-awaited spin-off, and with European security company Securitas, which spun off its security monitoring business, Securitas Direct. In both cases, the market responded favorably to the moves.

Brinks has a home monitoring and alarm division, Brinks Home Security, and a separate armored car and cash services business. MMI believes the company would best be served by separating the two businesses into different companies.

Lifflander complained Brinks has taken no action on the matter despite repeated demands from stockholders. Both MMI and fellow hedge fund Pirate Capital have pressed Brinks to pursue strategic alternatives.

“We fear that the public markets are passing BCO by, to the potential detriment of all its shareholders,” Lifflander wrote.

MMI believes a tax-free split-up could make the company’s stock worth more than $79 per share, an increase of about 26% above recent levels. The company’s shares traded higher the day after MMI sent its letter.

Currently, MMI owns more than 4 million shares of Brinks, or about 8.3% of the company. Pirate owns about 8.6% of Brinks and fellow hedge fund Steel Partners owns about 8.0%.