Depending on who sent it, the quantity mailed and the level of automation, there is a discounted rate of 10-cents for Standard Mail Nonprofit Automation as shown here:

Incidentally, the MPP postmark from ZIP 84199 is from Salt Lake City, UT. I have a couple of similar ones in my collection. I think it may be a large volume mailing house that contracts their mailing center services to any number of organizations.
No matter what the content, the stamps are certainly a "keeper" with one of them being a PNC. Of course, assuming it is a nonprofit rate, I think the mailer could have chosen to use a Nonprofit Org. stamp (i.e. Patriotic Banner or Snowflakes) also valued at 10-cents, but that option is left to the sender.