Since they were silver certificates he could have redeemed them for a 26.73g coin composed of 90% silver and 10% copper. In 2026, the value of the silver has fluctuated between about $46 and $94 (and the value of the copper content has stayed a little over 3 cents).

Those stopped being redeemable for silver in 1968, so their value is no longer defined by the metal prices of 2026.

If you swap them in stores, maybe. But taking counterfeit bills to the national bank is just stupid, even if very well made.