Expanding on carrier initials, when I see three letters or initials, checking the "Official Register" volumes is useful to ID matches to employee names.
The circled CPM matches with Clie P. Maffet at Marion, Indiana, who likely provided the directory assistance to forward the card to North Manchester.
The circled ACJ matches with Arthur C. Jones at Logansport, Indiana.
And no doubt these are carrier initials in the 2 auxiliary markings:
Such "fractured" mail often tells a more interesting postal history story than mail delivered without any difficulty.