Bought used, I've had for about 1yr. I upgraded my server and it now has 10GBE built in (Old server is listed)

This is will not work in a PCIE slot without the included adapter since it's a LOM standard and not PCIE. If you use one of the below servers the adapter is not needed.

I have only ever used one of the slots on the card but I assume the other 10GBE slot works.

Technical part name is 561FLR-T

The HPE Ethernet 10Gb 2-port 561FLR-T Adapter is a dual-port 10GBASE-T adapter, featuring the 10Gb Intel X540 Controller inFlexibleLOM form factor designed for HPE ProLiant Gen8 rack and tower servers. The HPE 561FLR-T Adapter delivers full line-rateperformance across all ports with low power consumption, utilizing CAT 6A UTP (Or better) cabling with distances up to 100 meters andis backward compatible to existing 1000BASE-T infrastructure. Providing high performance Ethernet connectivity, this adapter is idealfor virtual server and cloud computing environments