Not common, but you’re bound to encounter it eventually; associated stock code: Berkshire

Main body

Some stock codes contain “.” or other special characters, and when submitted to Interactive Brokers (IB) via the “Fix” report, certain conversions of the stock code names are required

BRK/B -> BRK B

Regarding Interactive Brokers, it can be analyzed to determine that the conversion rules are fixed and can be implemented through coding. When the rules are not fixed, the system generally needs to store corresponding mapping relationships, which business operation personnel update periodically.

Reference link

How do I enter the symbol for Berkshire Hathaway Class B shares onto TWS?