Stamped vs. Paper numbers....

If your frame/bike has both they mean different things. Peugeot would use the same frame for many different models.

Stamped numbers: Individual frames were stamped prior to being built into complete bicycles. If a frame has a serial number formatted A123 45678 Then 'A' represents a mystery, possibly the factory it was built, while '123' represents the year month, 312 would be December of 1983 and the remaining is the sequential build number. This format at started someone around 1978 and was phased in.

Paper number: Model specific. Nobody knows how the long numeric number breaks down but its some sort of identifier/sequential number. The alphanumeric code is model specific. For instance PH10LE P=Peugeot H=internaly brazed/HLE tubing 10=race LE='high luxury' Think of the suffix as the 'trim' code like with cars. And then followed by the frame size in CM.

Very special bikes like the 100th Anniversary model have matching stamped and paper serial numbers.