Eames fiberglass armchair question  

If you're planning to sell it,
how about leaving it as is and disclosing condition up front? It's only my opinion, but I'd rather you do that than than try to tart the chair up for eBay photos. Leave any attempts at restoration to the buyer's discretion, I say.
If you're keeping it to use, I'd recommend wet-sanding to the finest practical grit followed by buffing with polishing compound. Penetrol is a short-lived treatment, IME.

tktoo, which polishing...
tktoo, which polishing compound do you use for fiberglass? And the reason I said penetrol because it seals the fibers in. Does polishing does the same thing too?