Well, you were the one who chose him to support your position. So was he expressing his true beliefs in 1865? Or in 1869?
I don't recall stating my position, just a quote that conflicted with yours. But since you ask, I expect that Chase's more studied position on secession occurred in 1865 amid Francis Lieber's investigation into the probability of a successful treason trial against Jefferson Davis (Lieber concluded the Feds would lose).
It seems that you agree with Mr. Chase's changed position, which is fine. I know you to be a strong conservative, so I really hope you don't resort to liberals' favorite insult, used whenever a conservative justice does something they approve of, and say that he "grew" in office. Mr. Chase had absolutely nothing to lose in 1869 by changing his stated position on secession via an obscure Reconstruction-era bond case.