They're just aged as far as I know, Phil. I bought them both from Willcutt Guitars in the USA.
I first heard of Chad Underwood as a small-scale builder of relic Fender copies, very much like a US equivalent of Bravewood. I started watching eBay for his guitars and just happened to see the Junior on my 50th birthday last year. I couldn't resist! Then a couple of weeks later they had the Special and I thought what the hell....
Willcutt still have Underwood-aged guitars in their eBay shop occasionally. Nearly always Gibson Historics but I've also seem a couple of PRS models, there was an antique white DGT if I remember right.