" the first letter of the serial number indicates the production version of the amp"
Yes, but upgraded units will also have the letter of the iteration added to the end of the serial number. Sorry, I am uncertain what letter indicates the change to "evolution". So, "evolution" lettering under the Ayre logo is the easiest way to know but a call to the factory (or distributor if you're not from US), with the serial number will confirm whether the unit is "evolution" upgraded.
Yes, but upgraded units will also have the letter of the iteration added to the end of the serial number. Sorry, I am uncertain what letter indicates the change to "evolution". So, "evolution" lettering under the Ayre logo is the easiest way to know but a call to the factory (or distributor if you're not from US), with the serial number will confirm whether the unit is "evolution" upgraded.