Yeah, looks for sure like an aftermarket A/C kit. Not having seen enough of the slider heat controls in these trucks as for us down here in TX they are rare as hen's teeth, I couldn't say if the slider panel is factory or aftermarket as well. The "max" function on it is puzzling, wouldn't expect to see that on a heat-only panel, so I'll have to throw a wild guess out that the whole setup is aftermarket - not just the separate A/C button underneath the panel, but the slider panel as well. Could also be "dealer" installed A/C.
Edit - if you do go take a peek at it, please get a pic of the SPID label if it's still legible at all, and any possible pics of the A/C components such as compressor, bracketry, lines, etc. for comparison to the usual factory pieces.
Richard