A big issue of just picking up random vintage tubes, rebuilding them, and selling is that who knows which tubes will sell and which won't. Also if that came to pass someone who has a rare or uncommon tube that they don't want to send to France would have to sell their tube to the ETF, hope the rebuild works, and hope they can buy it back without someone else getting their hands on it first.
I do have a down to air 17" monochrome rectangualr I salvaged from a junker which I'd like to give them for practice, and to get it out of my garage.
