The PDF should teach you how to read the marking. Often, the top line is the device code, and the bottom line is a date/lot code (usually a 4-digit year/week). A good book clarifies which is which.
: This is one of the most famous online databases, often cited as a definitive "piece" of the SMD puzzle. It allows you to search by marking to find the actual part number and manufacturer. You can access it via the SMD Codebook website. smd code data book pdf
A technician in an industrial repair facility received a servo drive with a burnt component marked "A8W." No schematic existed. The manufacturer wanted $5,000 for a new drive. The PDF should teach you how to read the marking