SK Hynix 16GB ECC registered DDR4 DIMM, in good condition, tested and working.  These DIMMs are OEM SuperMicro, according to the warranty label.  (Warranty status and applicability is unknown.)

ECC registered memory, 2Rx4 layout.  Standard 288-pin DDR4 registered ECC memory.  It says PC4-2400T-RB1-11, and I'm not sure what the last part means.

Tested with a full run of Memtest86+, as well as normal usage.

As always, this listing is for the exact model of memory shown, but not necessarily for the precise DIMM pictured.  Note that some of these have a little wear to the label, as pictured.