THE IIIR with oblong buttons is actually an IIIRS .. which have less volume still ..and are an 80's morph of the IIIR.
III's ..yes, I've had several, dry tuned them and they sound like fuel injected Corona II's.. very loud. The Wet tuning on the factory standard version is the preferred tuning for Vallenato or Contra dance ( which I have heard said and seen written in the UK .. who knows why, if you claim they call it country dancing ? Maybe to coax in Americans..)
The IIIR is muffled in volume especially on the inner row.. it progressively loses volume from the outside to the inner row. I would not want to play fast music on one .. ( even though many Vallenato players still use them ).. I find them perfect for internal mic'ing and playing repetetive riffs ala zydeco..