Yes this kind of markings if the item is a private purchase...but you won't find this kind of markings in issue boots.
For example, these are the markings you can find : 28 4 43 598 or 31 5 42 256
28 for 28 cms (lenght of the foot)
4 for 4 cms (width where the foot is narrower)
43 for the year
598 is a lot/contract number
You can sometimes find also the name of the manufacturer, like Rieker or Joutz, but barely with a logo etc...
From the end of 1942, the RBNr is adopted, so many footwear received this kind of markings (ex : 0/0056/0342 (which is just an example and not the RBNr from a manufacturer of boots)).