Breitenbach was a company brand (or design house) that manufactured various advanced ranged weaponry for the Yellowstone Demarchists. These included weapons that ranged from handheld rifles to far larger spacecraft-mounted weaponry.
Though prefects didn't carry around ranged weaponry as standard issue, during the second Clockmaker crisis in 2427, Field Prefects Tom Dreyfus and Sparver Bancal were authorised by Supreme Prefect Aumonier to carry Breitenbach-branded rifles.
In Aurora Rising (The Prefect) Edit
"Then we should move out right now," Dreyfus said, readying his suit for exposure to Yellowstone's atmosphere. He picked up the heavy bulk of the Breitenbach rifle and slung it over his shoulder. "Thank you for the ride, Captain. I appreciate the risk you took in bringing us this close."
"I'm not the one taking the risk here." Pell touched a control on this console then studied a read-out for a moment. "We're stable. You're free to cycle through."
- excerpt from Chapter 29 of the novel 
* * *
Nothing would be gained by waiting, Dreyfus knew. "Do it," he said, mentally preparing himself for whatever was on the other side. Sparver hit the control, then moved to stand next to Dreyfus, his Breitenbach rifle held doubled-handed. But as the door rose, it became clear that there was no one waiting for them on the other side. Dreyfus allowed the muzzle of his own weapon to dip slightly, but remained alert. The two prefects stepped over the threshold.
"Put down your weapons," a voice said. Dreyfus and Sparver spun around, but it was already too late. The muzzle of another Breitenbach rifle was aimed down at them from the intermediate-level balcony. With the weapon on maximum beam dispersal, Dreyfus knew, it could take out both of them with a single pulse.
- excerpts from Chapter 29 of the novel 
* * *
Sparver flipped open the Breitenbach's weather cover, exposing the muzzle with its delicate battery of plasma emitters and laser-confinement optics. He powered-up the weapon, mindful that the cutter might be sniffing the local electromagnetic environment. The weapon ran through its start-up cycle, then signalled readiness. Sparver settled the long barrel of the rifle onto his shoulder, bazooka-style. A portion of his faceplate filled with a sighting reticle, superimposed over a view of the rifle's current target. Sparver eased back on his haunches until the hovering cutter bobbed into the middle of the reticle. He squeezed a stud on the side of the primary grip, telling the weapon to lock on to this target. A red bracket pulsed around the cutter, signifying target acquisition. Instantly Sparver felt the suit stiffen and adjust his posture for him. The rifle had assumed command of the power-assisted suit; it was using it as an aiming platform, with Sparver just going along for the ride.
For once being a hyperpig had been to his advantage; he doubted very much that a fully armoured and suited baseline human would have been able to navigate some of the crawlspaces he'd had to pass through, especially not while dragging a Breitenbach rifle.
- excerpts from Chapter 32 of the novel 
"One Breitenbach three-millimetre boser with a proton-electron precursor."
- Antoinette while enumerating the humbler weapon systems installed into Storm Bird 
All of the crewed trikes carried some form of armament, ranging from single-use grasers to
gigawatt-yield Breitenbach bosers.
- excerpt from Chapter 34 of the novel 
- The name seems derived from a German family name. Literally translated into English, "Breitenbach" would mean "broad brook" or "wide stream".