sys51213

This module is a system-level package (SIP) module for Zigbee, Thread, Bluetooth 5.0LE, and dynamic multi-protocol (Zigbee + Bluetooth) connectivity.
It is built on the EFR32MG13 SoC (System on Chip).

Therefore, if the SYS51213 module you are looking for is related to wireless communication, then this module can be used as a reference.
To get the detailed parameters of this module, you can visit the official website of Silicon Labs.
Bluetooth module:
Bluetooth modules are also mentioned in the search results, such as those using the nRF51822 RF chip.
Therefore, it is possible that SYS51213 is a Bluetooth module made by a certain manufacturer.