The 1967/68 period was when the new owners of Fender swept away the classic ‘blackface’ control panels across the range, replacing them with a new and eye–catching silver livery.
Many models also received an aluminium trim around the speaker baffle to complete the ‘silver’ overhaul, although this element was soon dropped (you won’t find any of these dating beyond 1969).
Other sources to date your amp may include serial numbers and overall look and visual components on the amp as well.
Dating an amplifier by serial numbers can be effective as well.
Again, it's important to be sure the parts are original on the music equipment to get a valid date for the amp.
Well, this one uses unashamedly old technology, albeit with a bit of a twist, but it certainly scores very heavily on the latter point.
Fender’s Princeton model, the smallest of their dual 6V6–based combos, has been through a number of iterations in its lifetime, but it was the iconic ‘Blackface’ model that Fender chose to recreate as part of their Vintage Reissue Series.
The ‘65 Princeton Reverb reissue has gone on to become a best seller that, apart from its PCB–based circuitry, represents quite a faithful recreation of its highly regarded predecessor.