The 1858-S and 1853-O likely had PVC as both show corrosion. I don't see PVC on the Texas. What do you see on the Texas that makes you think that?
The discoloration is a similar Grey to PVC, there are some small green spots also. I don't think they are corroded, I think they could use some time in pure acetone.
A nice upgrade from my AG3. I couldn't resist this coin and am delighted to win it. Now I have to sell the other two to afford this one. PCGS VF25
I have very little Seated stuff in my collection right now. Here are some Ancient and World coins that sorta fit the "Seated" theme. Alexander the Great, lifetime drachm Tiberius, "Tribute Penny" denarius Caligula, VESTA as Nero aureus Vitellius denarius Great Britain "Cartwheel" twopence Peru, 100 soles, Seated Liberty type (1.3 oz. gold!)