When Jo is handed the postcard (supposedly from 9 years ago) there a 34¢ stamp on it. Postage, especially for a postcard and the date is was mailed, would have been much less. Also, there is no postmark over the stamp.
The Glock pistol used in the roof fight clicks multiple times, when the trigger is pulled. This type of pistol can't do that, unless the slide is racked before each trigger pull.