Following up on this, Terry Kurzinski, the dealer who sold the envelopes on
ebay, wrote an article about these in the March 2018 issue of The United States Specialist, entitled "New Find: Prexie Used 'Out of the Mails'."
In short, John Becker was exactly correct.
Included in the article, someone who purchased one of the covers from Terry on
ebay contacted the Galloway Co., which is still in business, and was able to get some historical context to the envelope and slips.
Additionally, in a later issue, a member submitted as a letter to the editor, the original ruling that applies to Milk Checks, as printed in the February 20, 1936 Postal Bulletin:
Quote:
MILK CHECKS. A check given in payment for milk is not a "letter" within the meaning of the private express statutes. If the check shows upon its face for what purpose it is issued, i.e., pounds of milk for which payment is being made, quality, test, price per pound, etc., it would still fall within the category of "commercial papers"; however, such data must be a part of the body of the check itself. Milk checks in this form may be delivered by contract milk haulers, or by any other method suitable to the sender outside the mails without the payment of postage.
However, a milk statement or settlement sheet, giving information relative to weight of the milk, quality, butterfat contents, deductions for hauling, price per pound, etc., when forwarded along with the milk check for the producer's information and retained in his possession, is a "letter" within the meaning of the private express statutes.
KARL A. CROWLEY, Solicitor