What was advertised in a colonial American newspaper 250 years ago this week?

“The Royal American MAGAZINE is likely in a short time to make its appearance.”
Isaiah Thomas, printer of the Massachusetts Spy, continued his efforts to solicit subscribers for a new endeavor, the Royal American Magazine, in the fall of 1773. Like many other projects proposed by printers, publishers, and booksellers, he would not take the magazine to press until his subscription proposals garnered sufficient interest to justify further investment. Thomas began with a brief announcement in his own newspaper on May 27, declaring that he would soon publish “PROPOSALS for printing by Subscription, The ROYAL American MAGAZINE.” On June 24, the proposals appeared in the Massachusetts Spy. Thomas may have also distributed the proposals as a separate broadside or handbill.
After inserting the proposals in his own newspaper, Thomas set about disseminating them to an even broader market by placing them in all of the newspapers printed in Boston as well as newspapers published in other colonies. In July, the proposals ran fourteen times, appearing in seven newspapers printed in Boston, Newport, New York, Philadelphia, and Providence. In August, the proposals appeared thirteen more times in eight newspapers. They ran for the first time in newspapers published in Hartford and New London. Along the way, Thomas, who had achieved a reputation for opposing the British government with the news and editorials in the Massachusetts Spy, issued a separate clarification that the Royal American Magazine “will never be GUIDED or INFLUENCED by any PARTY whatever,” despite allegations to the contrary. However, when Thomas began publishing the magazine in January 1774, it quickly became a vehicle for delivering propaganda that favored the patriot cause.
In September 1773, Thomas dispensed with running the lengthy proposals in the Massachusetts Spy in favor of a shorter notice that encouraged the public, presumably familiar with the project, to become “promoters of this useful undertaking” by “send[ing] in their names with all convenient speed.” He required “NO Money” until subscribers received the first issue, which he planned to publish “as soon as he hears what number of subscribers there are in the other colonies.” Thomas pledged that the magazine “is likely in a short time to make its appearance” thanks to “the generous encouragement of a great number of gentlemen in this province.” Through reporting that the magazine already had so many subscribers, Thomas leveraged existing demand in hopes of generating more demand among those who had not yet subscribed. To increase the likelihood that prospective subscribers would see and take note of this shorter advertisement, he gave it a privileged place immediately after the news in the September 9 edition of the Massachusetts Spy.