Differentiating and comparing MacBook Pro models across different generations

What details (such as dates/year, identifying numbers, etc.) distinguish 2nd generation 13″ MacBook Pro models from 3rd generation?

These 2nd generation models featured the older more reliable keyboard, power adapter, memory card slot, USB-A slots. I am shopping for a used device and would like to know how to differentiate one of the most recent devices of this generation (prior to the more problematic keyboard design, Touch Bar, etc).