I can't give a date for these but here is an example of their use in a postal training environment.
Although this appears to have been through the postal system, the clerk probably had to verify that the postal rate was correct, and if satisfied, cancel the franking. Note there is no date shown; so this was purely an internal exercise.
Amongst your small group, are a few 'postage due' test stamps as well. These may be somewhat scarcer.
The French training stamps are known as fictifs, and can be found in specialized France catalogs such Yvert & Tellier.
The bottom row are postage due training stamps. I'll ID those for you. The top 2 rows of stamps are a bit tedious to ID because there are over 200 denomination and color combinations and yours are all over the map. The great majority of them will be 1-2€ each. Doing a random check, they do appear to be from the various issues of the 1960s and 1970s, but obviously I didn't check them all. Maybe someone more familiar can help.
The postage dues in the last row are (Y&T catalog numbers):
FT23 20c (issue of 1972-1985)
FT16 30c (issue of 1965-1968)
FT26 30c (issue of 1972-1985)
FT13 50c (issue of 1961)
FT28 1fr (issue of 1972-1985)
All of the postage due fictifs were valued at 1€ in my 2010 Y&T.