100% chance. It was done as a spoof to mimic a precancel. Privately made and applied to obsolete foreign postage stamps to avoid getting in any trouble with the USPOD by using US stamps. A similar thing was done to Christmas Seals. There is a lot of non-standard and philatelic Santa Claus, Indiana material beginning in the mid 1920s created by the precancel collectors and others in the state, especially Indianapolis.
There are known "fake overprints" on US Stamps, too. It may have been illegal but probably not enough volume on low value stamps to make it worth the time and effort to prosecute those doing it. Nevertheless, it makes for an interesting oddity: