I think Oct 10 2011 was when they started installing the 30274 "Gen4" ejectors into the 9mm Gen4's. A Gen4 test-fired on that date or after should have all of the most recent parts. A Gen4 G19 should have a 30274 ejector and a guide rod that has "0-4-3" stamped on the metal base. One with a test-fire of Sept '11 should have the latest guide rod but if it doesn't you can contact Glock about exchanging yours for the latest version here:
They also started installing "dot" connectors into the Gen4's to give them about the same trigger pull weight as a Gen3 would have with the standard connector. I don't know when they started installing them but it was sometime before Oct '11. You can check to see if your connector has a "dot" marking by looking at the tab sticking up out of the field stripped frame, between the two red arrows in the picture below:
(the connector in the picture has a minus symbol indicating a so-called "3.5" connector)
If you don't see a dot marking on the connector tab, it's likely a standard connector. Glockparts.com sells "dot" connectors but in the "Notes" section with your order you must provide the first three letters of the serial number:
Put at least a few hundred rounds through the gun. If you notice any casings ejecting back at you, any failures to eject, or significant dents/scrapes on the case mouths of the spent casings I would install the 30274 ejector and/or replace the extractor with a new 9mm LCI extractor. If you don't experience any of those things, you don't have anything to worry about, leave the gun as it is.