Spinning off another thread, was the Wheatstone Mayfair built the same way as today's hybrid concertinas? I know that it used accordion reeds, but I don't know whether they were mounted flat or on blocks.
And then there's the occasional Bastari with flat-mounted reeds, such as this one.
And Andrew Norman was making the Saxon around 1980.
And Marcus says on their web site that they've been building concertinas since 1982.