https://wccftech.com/first-gen-amd-ryzen-cpus-are-appearing-with-12nm-zen-architecture/

The AMD Ryzen 5 1600 CPU arrived back in 2017 with six cores & twelve threads and was based on the 14nm Zen core architecture, but a new version of the chip has reappeared in stock, featuring the updated 12nm Zen+ core architecture.

The primary way to show between these two different models is the serial number featured on the IHS. The original CPU should show YD1600BBAE while the newer CPU will show YD1600BBM6IAF at the bottom of the CPU. This variant of the CPU is now making the rounds and features the Zen Plus cores which compared to the older Zen cores offer slightly better IPC (3-5%) and a few overclocking enhancements.