So it finally arrived from Germany (with a small amount of sand in the static-dissipative bag... wtf?) and I've mananged to get a good look at it. It definitely looks like some earlier ET3000AX models with the 5 crystals mounted to it. From a .txt document uploaded as a webpage detailing the switch orientation for a ET3000AX it appears I need to have all 4 switches to the "off" position to enable VGA mode, which leaves the 3 jumpers across the board. I've seen some details about IRQ channels and enabling/disabling the EGA port from other SVGA cards so I'm hoping they're in the correct position.
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There's also some damage to one of the tracks near the VGA port. I hope it's just topical.
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I've messaged the seller asking this card's story. I'll update if he knows anything.
So for the install, I've no idea if I need the 3000AX or the 4000AX drivers (or who knows... a custom driver maybe?). I'll experiment with them both to see what one seems better.