Thanks @albrt for posting all the Gitane bicycle information.

Member @non-fixie posted a date code stamping that was double struck.

The date code above is another example of double striking. You can see the top portion of "7" and "1" on the last two digits of the date code.

I do not know the mechanics of how the date codes were stamped or at what point in the build process the stamping occurred. My guess is that the dropouts were stamped before the dropout was assembled into the frame. The operators of the stamping machine could make mistakes.