The control panel, as seen in three closely-examined comms, comes in two thicknesses of aluminum stock.  It seems even with the minimal amount needed for these small pieces, Wah ran out of one size and started another.  In Alpha and Epsilon it is estimated as 0.032".  Zeta's is discernibly thinner, perhaps 0.016":

Photos of Delta and Gamma show they also have the thinner (0.016") aluminum.

In Delta a subtle left/right surface brush is seen; in Zeta it runs up/down.  Alpha surface brush is more random, though with a bit more left/right than up/down.  Gamma's TMOST pic suggest up/down.  Epsilon's has been cleaned recently, so its original appearance is lost.

Where to get:
These sheets are available in some hardware or hobby stores or easily online at metal sites.

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