There are two types of censor handstamps with numbers within a double oval.
If the top word is CONTROLE and the number is sloping it is a military censor, and I do not have any good data on where they were applied. Civil mail posted in a military area was likely to be censored by the military, eg in Alsace area.
If the top word in the oval is OUVERT and the number is upright that is civil mail censorship.
In this group the numbers were allocated in blocks but within the blocks there are gaps. The main groups were:
1-50 Dieppe, 51-100 Belfort, 101-200 Beaune, 201-250 Lyon, 251-265 Bellgarde, 301-350 Marseilles, 351-400 Bordeaux, 401-422 Bourg-en-Bresse, 451-500 Narbonne.
Part of the Marseilles block of numbers was allocated post-armistice to Salonika and Constantinople.
Groups from the higher numbers, 751 upwards, were allocated to Algeria Tunisia and Egypt and post-armistice to Beirut.
And you will know that 901-920 were allocated to London from my articles in the Bulletin.
I hope this answers your questions.