Prepping my 59 cab to paint next week. I have 4 holes (two on each side) & I'm not sure what they are for.

This truck was a maintenance truck for the state of California. My best guess is an attachment for a window shade

Anybody seen this before? THANKS
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20210629_142632.jpg (96.71 KB, 212 downloads)

1959 3100, original 235/3 on the tree w/overdrive. Carter YF 2100S carb, 205/75/15 w/front sway bar