I have a SOT-23 SMD component marked \$\underset{\bullet}{\vert}3\bar{\textrm{S}}\;\bar{4}\$ as shown in the following images
I managed to find out that \$\textrm{3S}\$ stands for MMBT5551 NPN transistor. But I couldn't find the meaning of the prefix \$\underset{\bullet}{\vert}\$ and of the \$\bar{4}\$. I appreciate any help you can give me with it.