As for the stamping itself, that workstation was having a bad day.
The top row cut into the wood fibers (which is why the letters are dark --- stain wicking is the culprit), and the bottom row has several double-stamped characters (which isn't all that rare, but these are WITHIN the word, not the entire word, which is truly strange).
Given all that, it looks like the guy might have realized after finishing everything that he'd used a "1" instead of the correct "0", so appended it.
Extra digits in ascending order aren't uncommon (it's a "warranty update" thing), but to go backwards in time wouldn't happen except in an error situation.
All of which doubles down on the 1970's stem guess. Dunhill's Great Reset during that time caused all manner of cost-cut-intiated screwups that manifested in the final product.