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C = 1960's
5 = 5th year, thus 1965
O = Fairlane/Torino
E = Engine (as in engine parts or engine engineering dept)
Since it was possible to get the 2v, 4v or hi-po 4v 289 in a Fairlane in and for some time after '65, that's about all you can figure with that bit of info.
Numberdummy can tell you how many different pistons there were, and I'm guessing there were two.
Yep. Those C5OE 6110 H pistons are the 4V versions with an advertised 9.8 compression ratio in late 1965 production. I believe those pistons were used until 1967, but the compression ratio will be different if different size combustion chamber heads were used in those years.
As an aside, early 1965 4V pistons had no valve reliefs so gave an advertised 10.0 compression ratio.
1965 2V heads had a small dish, and starting in late 65 also included valve reliefs.