I have recently developed a "thing" for the S&W 39's. So far, I have acquired two almost NIB's 39-2's and thought you might enjoy what I have discovered. The earlier one was manufactured in 1973-74 and the other in 1981. Now for the differences. While the boxes look identical at first glance, the older box has SMITH & WESSON, 9MM AUTOMATIC PISTOL, (DOUBLE ACTION), BLUE FINISH - Model 39 embossed on one end of the box top in silver print. The later box does not have this, and instead has a printed label that reads, 0392014001, MOD 39 9MM AUTO 4IN BL glued to one end. (Also has a "Y" floating around by itself.) Both have the upside down glued regular label on the other end. The older box also has the Statement of Liability and Warranty printed on the inside of the lid and dated April 15, 1955. The newer box does not.
I also noted that the older pistol has PAT'S Pending stamped under the ejection port while the newer pistol is blank. The slide locking notch is also deeper on the older pistol than on the newer one.
Thought you might enjoy those observations.