Isnt ‘V’ a Quinarius (5 Asses), an ‘S’ a Semis (Half-Ass), and I’s are an As. so... my dyslexic logic feels that 2 RR Sestertii (or SII as a denomination - which means 2Asses and a Semis or 2-1/2 Asses) = a V or a Roman Quinarius.

I thought 5=6-1 was too obvious, so I was trying to work this out like @Alegandron (I enjoyed your solution Brian)

It is not a 1, it is an i the symbol for the square root of -1. But I would with the sesterius and asses, but it does not add up.

LOL, like every thing they did in the Roman Empire, it DOES add up when they want to MAKE it correct for their ends. It only takes creativity... and I DID explain that I truly am dyslexic. Thank you @ancientcoinguru