The Brown card was easy because he was only found in the Koesters set--he wasn't printed at all by the American Caramel Co. as part of either the E121 series of 80 or 120.
The Hoyt was printed in both sets. The fact that they were found together probably means that the Hoyt is in fact a Koesters card (blank backed) but it is also entirely possible that the Hoyt could have an American Caramel back if it were to be soaked--as I can't tell through the thick paper if there is any printing on the back. So in short likely a Koester's card BUT it could be a E121 Series of 80 (if it is somewhat thicker) or E121 Series of 120 if the card is thinner (120 series was printed on thinner stock than the series of 80).
-Rhett
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