![1999 vs 2009 [4032x3024 - 2MB]](https://pic8.co/sh/w8aboz.jpg){kind=link}
To be slightly pedantic ... DIP ... Dual Inline Pins. (So, not a DIP as they are surface mount pads and not Inline...) :)
Your 2nd hypothesis looks to be correct. It's labeled "J1", likely a test / programming connector. Looks like there are pogo pin marks where a fixture came down and spring loaded pins touched the board. Looks like the center hole between the pads is an alignment hole for the header.
Looks like a few of the lower right pins are connected to power buses. Looks like there is some more junk (burned flux, oxidation, etc.) on those pins from the higher current across those pins/pads to power the board while programming / testing.
Just my guess...
2009 had a piece of foam over the top of the components. That's both residue from the foam and corrosion from the interaction between the foam/glue and the chemicals in the environment the drive was in.
Lol! Right, surface mount (if those pads were meant for a device). I never got involved in board test, but that seems like a lot of wasted real estate just for board testing 20 probe pads. I worked at the device level throughout my career, was never involved in board test so I'm not claiming expertise in board testing, just curiosity.
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