Probably not too common although on the day yours there may have been a number more as it appears someone inserted the ID plate upside down on the pattern.
I believe I have the process correct, positive patterns or pattern boards were used, for making negative sand molds... the patterns or boards have areas for part numbers and casting dates to be changed (sometimes the ends where the screws are located -which hold the number plate- are transferred into the green sand and show up in the casting).