Constantine I brockage with unusual line across reverse

[Victor]

 I have had this coin for quite a while and just got around to taking a photo and noticed something unusual. The reverse of this brockage has a line running under the portrait. Any ideas?

21mm   2.9g
IMP CONSTANTINVS P F AVG

 

 

[Heliodromus]

The photo is playing tricks with my eyes - I know the brockage bust must be incuse, but it doesn't look that way ... What about the line, is is raised or depressed ?

The line isn't on the obverse, so can't be on the die, and must be from either the stuck flan (who's obverse struck this one), or the flan of this coin. If the line is raised then it must have come from a scratch/depression on the stuck flan, else if depressed then from the flan of this coin. It's odd though - never seen anything like it... doesn't really look like a scratch/gouge.

[Victor]

The line is also incuse. It's a real puzzle.

[Heliodromus]

The only "explanation" that seems to fit the evidence is that this was an existing gouge across the flan before the coin was struck, which was then obliterated in the bust region by the bust of the coin stuck to the upper die pushing down in that most deeply recessed area.

Not sure why/how a blank flan would have a gouge across it like that though?

Is there some other explanation?

[Victor]

Yes, I figured that the flan must have been "scratched" before striking; though I can't imagine why it was done. It also doesn't seem to have been done accidentally. The best mysteries are tough to figure out though.