I own three of them and don't know a whole lot, and just about all I've learned is from these boards. Estusa is based in The Netherlands. Apparently they bought the Power Beam molds from Puma or from Becker himself, I don't know. I did not play and was out of touch and not a fan or paying attention during the 80s and 90s when Becker was playing. He and a few other used frames similar to the Power Beam series, and Becker may have had a hand in designing them. The ones I have were made in Taiwan and purchased from Tennis Warehouse.
Will someone with knowledge about this please step up? Inquiring minds wanna know ...