pistol vs. sbr

First time post, long time reader! I purchased the SAINT® VICTOR .300 BLK AR-15 PISTOL last year. After the ATF letter, I’m confused if I need to purchase a SBR stamp or if I can modify it to still be legal according to the ATF. For reference, mine is still stock, with the exception for Sig...

It seems like when I bought my Saint Victor 556 Pistol with a SBA3 brace that there was a letter or certificate that it was all good with ATF (in the pistol designation... and NOT a SBR) ... does anyone know if this correct and if so where one could find that? Seems like Springfeild would've...