Question. there are a number of RF Extenders around for both Pronto and Marantz and they are listed as being US or EU versions but I would like to know if they really are physically different or is it just a marketing jargon.

There is the Phillips RFX-6000 (US) and LI900 (EU)
or the Phillips RFX-6500 (US) and LI910 (EU)
Marantz love to confuse everyone by only have one model for both markets
RX-77 both (US) and (EU) version (2nd question how can you tell which it is?)
RX-7001 both (US) and (EU) version (2nd question how can you tell which it is?)

I have a EU remote but can get a US extender much cheaper, I question if the Extender can except both RF frequencies (433Mhz and 418Mhz) since Receiving a Frequency is not the same as sending one when it comes to FCC rules.