Provisional Overprint?

Here's another puzzler for everyone. I can find no reference on anything to do with the overprint on this stamp. I've checked everything from Brookman on. Any ideas or information would be greatly appreciated.

The letters appear to be on top of the cancel. Does anyone remember rubber stamps where the letters could be inserted individually into a slot to form words?

That was the first thing I checked. I can't show it here, but when you hold the stamp at an angle with a strong light shining on it, the cancel is what is shiny and appears to completely cover that part of the overprint. This was what made me start looking elsewhere as my first thought was this was a fantasy someone had created after the fact.

If the overprint was applied later than the cancel, I should have seen the ink where the letters of the overprint did not soak into the stamp and the cancel.

So, any ideas anyone?

Looks like an older typeface and ink color.
I'd wager it was a youngster, maybe even adult, playing around
with a common used stamp.
Not philatelic nor likely to have any connection with the denomination or value of the stamp.
Junk but 'fun' junk.