PSA declined to designate this card, with a partial "a" visible, the error card. We're aware that there are degrees of the "a" visible and at some point there is a cut off for what is and is not considered the error. That being said please see the images. The PSA 8 is the card from PSA's Card Facts Page.
https://www.psacard.com/cardfacts/baseball-cards/1958-topps/pancho-herrera-herrer-433/26468
If that's not a match for the exact same amount of "a" as on our example I'd like to know what is. So according to PSA this is NOT the Herrer error, it just looks exactly like the one they use as their exemplar...