The commercial models didn't have the letter prefix serial # on the side, and sometimes had the serial # in different places. look under the barrel, with the cylinder swung out, etc. Either way, most commercial made French ones were not provable as antiques, therefore no letter. As well, as has been mentioned, Belgian copies wouldn't follow the norm either. I know most Belgian guns didn't come with serial #'s before the turn of the century. Does it have any Belgian proof marks, especially on the rear of the cylinder (ELG in an oval with a crown above) or anything like that. If you do a search of Belgian proof marks, there are some good sites that'll show you what to look for. It dosn't sound like you can prove it is an antique however, so I doubt it's what you want. Good luck