~~~ where any damaged or worn nacre had to be removed from the tables and replaced.

That may explain why we sometimes see different style engraved serial numbers because I do know even today that new orders / reorders of an existing series follow with the last number of the series.

The law has been mentioned a few times on eBay, but I would still like to see it in writ to find out the demand of time for replacement or if time was not part of the demand because this might be a reason why we sometimes see two or more denominations of a series in either different size or shape which may have been decided by the manufacturer using whatever stock inventory they had available; especially if many pieces of a certain denomination were needed which, might also mean that the serial numbers meant more than what we think and not just for casino control.