Unfortunately if the maker didn't keep track of serial numbers there isn't much hope that you will be able to determine the year by that method. Due to the fact that the second link I shared above can't determine if it was made by Joseph Marechal or Jacques Marechal I wouldn't hold out much hope for determining the year by serial number. The only other possibility is if there is some sort of a mark on the gun that can be proved to have only been in use in 1897 or earlier.
This gun is a really good example of how ridiculous some of our laws are. There is a pretty good chance it is a prohibited piece which few people may own.
I'm doubly saddened by this as I own an FN1922 in .380auto with the Dutch crest on the slide (a restricted firearm and last in the list of my first link above) and it would be nice from a collectors point of view to own the revolver that it replaced. The only option would be to have it deactivated which would be a crime.