Hello once again!
Here is another tip for you :
You will notice that on French websites, like GeneaNet, Genealogie.com, and others, many (most?) French genealogists now put two digit or five digit code numbers after the names of cities throughout their family trees. (There are several software packages from France that do this automatically.) This code number is not critical if the name of the département is identified. However, modern French websites and genealogy software packages allow genealogists to search using these code numbers - which is quick and easy, so it is becoming quite useful. --- You may want to consider adding them in your computer software or websites.
I am writing this message because I want to help you understand exactly what these numbers are:
If you see just two numbers, these are the « département codes ». (There are 101 départements in France; 2A and 2B are for the two départements of Corse / Corsica.) Everyone in France knows these codes, just as British and Canadians know their two letter province abbreviations and Americans know their state abbreviations. You may be familiar with a few from your research already, especially:
17 = Charente-Maritime
44 = Loire-Atlantique
85 = Vendée
The 5-digit number is the « INSEE code ». Each of the exactly 36,700 communes in France (on 1 Jan 2012) has a unique identifying code number. -- ***It is very important to know that INSEE codes are NOT postal codes! One French post office may serve several tiny towns, so postal codes are not unique for each town, although they might appear very much the same as INSEE codes because they also have five digits. Only INSEE codes are used in French genealogy.***
The first two digits of the 5-digits INSEE code are the département number. The remaining three numbers were assigned alphabetically by the government by département.
You can easily find the 5-digit INSEE code everywhere. Perhaps the easiest and most familiar place for you to seek them is Wikipedia. ---- Simply go to Wikipedia's website, and enter the name of your French city, then look at the InfoBox in the right column and there you will find them.
For example, for Montreuil, Vendée, you will see:
INSEE/Postal Code 85148/85200
...and for La Rochelle (Charente-Maritime), you will see:
INSEE/Postal Code 17300/17000
For your genealogy, you will enter 85148 and 17300 in your family tree software, if you are so inclined.
Since you have become an « expert », going to websites of French archives and reading ancient Middle French and Old French handwriting from the 1500s and 1600s like a true professional, I thought you might find this useful to know.
Bonnes recherches !