In addition to all of the above, there's also the fact that there's a ZIP code anywhere in any address on the box.
Postal codes - a city name followed by a number - came into use by the US Postal Service in 1943. ZIP codes were a later invention, introduced in 1963, as was the standardized two-letter state abbreviations we commonly use today. They became mandatory for use on certain classes of mail in 1967, and in 1983 they introduced the "add-on" ZIP+4 codes, further parsing one's location to a single set of digits. Companies like USPC would likely have started using ZIP codes on their packaging around 1967, and certainly not earlier than 1963. ZIP+4 codes aren't as commonly used on packaging but they're out there - I just haven't seen USPC use them on their deck boxes yet.
Little details can sometimes help in dating a deck!