@the-accumulator according to experts in this forum, it's 1931 or 1932 due to the Pat Appld For tang stamp on the pile side. According to
@zzyzzogeton in a previous thread:
John,
The Mountaineer is the 43 pattern. Your model looks to be a 643, the bone stag handle version.
Your knife was made in 1931 or early 1932 - based on the pile side ricasso stamp "PAT APPL'D FOR".
Western applied for the double tang patent in 1931. Some time in mid/late 1932 to early/mid 1933 (no specific date has ever been identified), the stamp changed to "PAT PEND" or "PAT PENDING" when Western received notice that the patent application had been approved but had not yet been issued.
The patent was actually issued in 1934 and the ricasso stamp changed to PAT'D or PATENTED. At some point in late 1934 or early 1935, Western added the actual patent number - 1,967,479 - to the stamp.
The patent number was dropped from the stamps around 1952.