The Post Office will get it's penny:
(From the PDF on the Auxiliary marking website )
"The growing use of return addresses in the late 19th century, on both business and personal mail, generally favored Returned for Postage over Held for Postage markings. However, an upsurge in Held for Postage mail coincided with the "Golden Age" of postcards, from their acceptance in 1898 through World War I. Since post cards typically do not have a return address, they are prime candidates to be held for postage if unpaid or short paid. Violating one of the unique post card rules,
such as writing across the center-line, turns a properly paid post card into a Held for Postage letter from the prospective of postal regulations"
Lots of information here on Auxiliary Markings.
https://www.postal-markings.org/Dropped off to the Los Angeles PO and postmarked on June 2, 1909.
Eagle eyed clerk spots the violation - crossed the line (at top)

, and wacks it with a "Held for Postage June 3 1909" auxiliary marking" and stamped "DUE 1 CENT"
Poor Miss Freda (as recipient) was about to get a notice saying she must mail (2¢ more to mail back?) 1¢ in postage along with the notice back to the PO to release her as yet unknown mail.
Miss Freda must have wanted it because on June 11 LA PO applied her postage and a "This is the mail for which you sent postage", red lined the "DUE 1 CENT" and sent it on its way to the San Diego General Delivery where it arrived on June 12.
Hopefully after all that, Miss Freda was able to pick if up at the General Delivery window.
Moral of the story is - "Don't cross that line" or the PO!

.
As a bonus I have a nice card showing usage of both the old(1903) and new(1908) Franklin 1¢ General Issue on it.
Best to all,
pat
