That Breaker (Siemens BQ) is what's known as a "Feed-Thru"
It's typically used for Tapped Circuits on Buss Duct, Switches in MCCs, and when an Enclosed Circuit Breaker type Switch is used (like for a Disconnecting Means).
As far as I know ("AFAIK"), they are not intended to be used in Panelboards, as they do not line up correctly on the Buss kit (proof being provided by the image above).
The Siemens "BQ" Series Breaker, is sometimes mistaken for the Siemens "BL" Series, which IS a Panelboard type Bolt-On Breaker.
If anyone ever has to add Branch Circuit Breakers in a Siemens P1/P2/P3 Panelboard for 240V maximum Circuits, be sure to verify the Breaker _IS_ one of the "BL" Series (BL = 10KAIR, BLH = 22KAIR, HBL = 65KAIR), before you leave the Supply House!
The BL's will have the Buss Terminations at the lowest point on the Frame, plus the terminals are Buss Aligned (have an offset).
The "BQ" Series (BQ = 10KAIR, BQH = 22KAIR, HBQ = 65KAIR) has "Straight" Load-Side Terminals coming out of the center of the Frame.
Nevertheless, I am stunned that someone would install the Frame as shown in the image!
p.s. Just noticed the Installer clipped the barriers at the Line Side Terminals!
[This message has been edited by Scott35 (edited 12-16-2006).]