Loaded MacPro3,1 (2008) with dual 2.8 Ghz Intel Xeon quad-core processors and 32GB 800MHz FB-DIMM RAM.
Upgraded with a NVIDIA GeForce 630 GT Metal-capable graphics card, with one DVI and two DisplayPort outputs. You'll want to use the DVI port for boot screen video output (especially if you're going to experiment with newer macOS installs.) DVI to HDMI cable included. More upgrades: four-port USB 3.0 card, and two-port USB 3.1 Type C card.
One 2TB HD in drive sled 1, booting into macOS 10.15 Catalina via Catalina Patcher, with OpenCore boot loader installed and ready for you to experiment. Drive sleds 2 and 3 come with AdaptaDrive mounts for 2.5" SSDs or HDs (silver mounting screws attached for safekeeping.) All four sleds are in great condition with all of their screws and grommets.
FireWire 400 and 800 slots, multiple built-in USB ports (one rear USB port disabled), 2 Ethernet ports, optical audio i/o. Two DVD burners installed, but they're finicky, and sometimes require manual help to open and close. YMMV.
Apple USB keyboard with number pad and two-port internal USB hub included, plus a USB mouse.
I bought this in 2013 and used it as a an all-around computer and digital audio workstation through 2021. You'll see that the side panel is a little battle-scarred, but it's completely functional. And if you're looking at this, you probably know, but these machines are tanks (both in durability and weight) and will happily run macOS, Linux, and Windows.