akela-one,
https://www.stampcommunity.org/uplo...IMG_5235.jpg ... Your phonograph advertisement is of particular interest to me. I am probably the only collector you will run across who actively seeks postal cards with pre-printed typographic commercial messages. I love to see the ways in which goods moved back in the day when long distance phone calls were an intolerable extravagance.
I also love the fact that these cards are cheap. Pre-printed commercial messages might as well be considered vandalism, and detract greatly from the price/value of a card.
The big exceptions, of course, are 'graphical' advertising cards, and the postal cards overprinted for the Great Exhibitions in the late 19th Century, eg, before the widespread adoption of picture postcards.
Once upon a time, I walked into a stamp store, explained what I was seeking, and asked to run thru their postal card inventory. They explained that they would never sell these cards over-the-counter precisely because they were such a cheap way to bulk-up the 'special surprise' cartons of philatelic material they sold to collectors on a regular basis.
One man's delicacy is another man's fiber supplement!
https://www.stampcommunity.org/uplo...5163_opt.jpg ... the first few covers you posted were posted from smallish towns in New York State. Some folks collect everything they can find from a particular town, most often their birthplace.
https://www.stampcommunity.org/uplo...5166_opt.jpg ... this cover bears a 'flag cancel', which is a well-established collecting specialty, with reference material available to tell you which style was used when & where.
https://www.stampcommunity.org/uplo...5173_opt.jpg ...
http://www.metropostcard.com/publishersm1.html ... that "M P // Co" logo belongs to the Manhattan Post Card Publishing Company (1928-1974). Once you decide that the stamp & postmark are "common", turn that card over and see what you've got!
https://www.stampcommunity.org/uplo...5172_opt.jpg ... "REGISTER OR INSURE VALUABLE MAIL" is one of a zillion slogans that have been used by the USPOD/USPS over the years and, in fact, it is easy to find this slogan being used by other postal authorities in their respective languages and, yes, slogan collecting is another active specialty.
https://www.stampcommunity.org/uplo...5170_opt.jpg ... researching the post-WW1 "CITIZENS MILITARY TRAINING CAMPS" has been on my ToDo list,
the place were tasks go to die.
You've got a lot of interesting things here!
Cheers,
/s/ ikeyPikey