We use the STM32F100VC for one of our projects. We were able to order devices marked as STM32F100VCTB (Revision A) and the STM32F100VCT (Revision X). Based on the ordering information of the device the letter "B" stands for "internal code". The errata sheet of the device is only valid for device marked with internal code B. We are not able to find any information about the internal code B and what the difference would be between devices which are marked and which are not marked. There is a difference because the UART1 of the marked devices works and the UART1 of the unmarked devices fails. Has any body any idea for what the internal code B stands and why devices could be ordered with and without this mark?