Not usual for multi voltage option to be included on USA market equipment for some reason, mainly Europe, but this isn't to say yours won't have this.

It could also be the case that someone has rewired the transformer to run at 110V as I believe this is possible but not 100% certain.

Welcome to Beoworld🙂

Chris.

Let me add my welcome to Beoworld.

I have reviewed the power supply circuit of the pentas and as you can see below it uses transformers with double windings meaning for 220 volts the windings are in series and for 110 volts they can be put in parallel, however there is no actual switch, this is something which would be done in the factory. You may wish to look at the 4 digit "Type" number because the US version is type 6603

Any thought on the level of challenge of rewiring 240v for 110? 

 I obtained an extraodinarily well-priced pair of 6632 at an estate sale (some cosmetic issues to the case, but the drivers are pristine, and the amps light up green when connected). I understand that to upconvert 110 to 240, each Penta needs 300w, which means an upconverter of 900w or more capacity. That's a shoebox-sized upconverter for each speaker, at $75 each. Makes the rewiring attractive even if a bit of effort is needed.