While the panel manufacturers will tell you that you can only use thier listed breakers in the panel, that is not correct and is one of the reasons that 110.3(B) only applies to instructions that are part of the listing and labeling. 110.3(B) does not require compliance with manufacturers instructions. There are UL "classified" breakers that are permitted to be used in panels made by other companies. The use of these "classified" breakers is code compliant and does not void the panel listing.
See UL Guide DIXF. "This category(DIXF) covers Classified molded-case circuit breakers rated 15 to 50 A, 120/240 V maximum that have been investigated and found suitable for use in place of other Listed circuit breakers in specific Listed panelboards." Note that classified breakers are required to be supplied with a list of panels that they can be used in.
Don
[This message has been edited by resqcapt19 (edited 09-05-2003).]
