Square Marcus Aurelius Sestertius?

[Connect4]

I have assumed, given the size of the diagonals, that this is struck using a Sestertius die?
However, there must have been issues of its being somewhat underweight?
 
Obv. Marcus Aurelius laureate head facing right [MANT]  ONIN   [VSAV]   GARM   [PARTHMAX]
Rev. Victory advancing left, holding a wreath and a palm S - C

Square flan 25.3 by 24.5mm, diagonals 32.3 by 31.7mm: axis 12hr: 13.9gr

Any thoughts on the unusual coin?
Thanks

[Connect4]

I have assumed, given the size of the diagonals, that this is struck using a Sestertius die?
However, there must have been issues of its being somewhat underweight?

Perhaps it was considered to be an AS?
 
Obv. Marcus Aurelius laureate head facing right [MANT]  ONIN   [VSAV]   GARM   [PARTHMAX]
Rev. Victory advancing left, holding a wreath and a palm S - C

Square flan 25.3 by 24.5mm, diagonals 32.3 by 31.7mm: axis 12hr: 13.9gr

Any thoughts on the unusual coin?
Thanks

[Pekka K]

Regular sestertius shaved to 3 nomisma weight.

Pekka K

[Connect4]

Thanks Pekka K, it's obvious when you point it out. 
I don't see any others but guess there will be other repurposed coins out there?
Thanks for your help

[Victor C]

Here my example of a square cut down coin. It is Constantine I with CONSTANTINIANA DAFNE reverse from Constantinople. It was cut down to weigh 1.5 grams (12mm) for use as a tremissis weight.