Over the past few days some weird chatter has hit the web, AMD would be shipping 14nm Ryzen 1600 processors, however no based on the Zen+ architecture at 12nm. They have the same IPC as the 2600 but slightly ower clock speeds, though boost behavior is still somewhat better than with the original 1600.

The 12nm Zen+ dies to seem to match Ryzen 5 1600 frequencies of 3.2/3.6 GHz, as opposed to 3.4/3.9 GHz specified for Ryzen 5 2600 - and since performance improvements over the "real" 14nm Zen based Ryzen 5 1600 are marginal, they probably did not want to confuse customers by creating yet another model designation, as they already have an OEM-only Ryzen 5 2600E rated at 3.1/4.0 GHz.

On Reddit it is reported that it is the 'AF' variants, getting tagged at 12nm. But it is not clear whether they are actually baked on the newer production process, or whether it is an incorrect report due to, for example, a new stepping. 

In Cinebench R20, the tested AF version of the Ryzen 5 1600 scores about 400 points higher than the original processors from 2017. With this score, the chip roughly comes next to its 'successor', the Ryzen 5 2600 , which was officially baked at 12nm . However, the chip tested by the Reddit user did not tweak rather well.

The new models can be identified by the serial number which is YD1600BBM6IAF compared to YD1600BBM6IAE of the previous variant

AMD might have replaced 14nm Ryzen 5 1600 processors with 12nm 2600 ones