I think you have other examples of this, which are called duplex cancels. The idea was that the target part (aka killer) cancels and prevents re-use of a stamp. The CDS (circular date stamp) part gives town and date info. That data is then (supposedly) easier to read. This was a fairly common type around this time.
This particular device was indeed probably all one piece. Newton may have had just a CDS for marking receipt of mail, but it was not necessary to use only that, only that the town and receiving time/date was given.
You might see covers with multiple killers but only one CDS. They still might be duplex cancels, where the clerk just inked the killer to cancel several stamps, then later struck the whole to get the CDS struck. Then you might see a portion of the CDS struck with each killer strike.
There were also duplex device versions where the CDS and handle had a ring attached so that the killer could be changed. This unintentionally allowed different carved/fancy cancel killers (that would wear out quickly) to be used by artistic clerks or postmasters.
Please keep the covers coming when you have the time and energy!
I just realized that I didn't post any covers that mention baseballl, at lest I don't think I did. Here are three cover / baseball letters as well. One mentions something called the "Black Diamonds" which I am wondering what that is or who it was. The last one here is probably one of my favorites because of the Train and the Snuff.
Here is a cover that looks like it has no stamp or even had one but yet it has something inside and it's sealed.... In the last image I held the envelope in the light and you can see something is in there.