There are other things in the world called "concertinas", and quite often those who know of those as "concertinas" know nothing of the English-made instruments which I consider to be a concertina (and vice-versa). The most extreme examples of these are the Bandoneons and Chemnitzers (distinguished by the arrangement of the keys, but otherwise similar.) Above is my chemnitzer, which was acquired when I followed a classified ad for a "Concertina". The midwest of the US sees a lot of these. Argentina uses the Bandoneon in tango orchestras. There are certainly other places where it is common.
I'm sorry to not have a photo of a Bandoneon for comparison (yet). The above photo shows the right-hand end, with the strap which goes over the back of the hand a little to the front of center. The orange-colored item is the air lever (which is not rusty, in spite of the appearance. I think it must be the alloy used which gives it that color.
The center of the button pattern is like a single-row anglo. The remainder of the buttons are arranged shotgun fashion. The placement must have made sense to someone at one time, and may actually be very convenient for playing in the keys of choice of the instrument, but since I am not a player, I am just confused. (There are sources of written music for the instrument, annotated with the arcane symbols to be found on the keyboard. (More about that later.)
The large-format version of this image shows some of the button markings (above and to the right of each button), showing some of the more bizarre markings. One which cannot be clearly seen is a "+" in a circle. This large-format version also make clearer the blue "mother of toilet seat" finish used on this instrument. I have seen some with a more normal dark wood veneer.
This photo also shows (though not as clearly as I would like) the bellows, including the two intermediate rigid frames. What is not visible from this angle is that there is a small metal ring attached to the center of each frame. It is intended that a neck strap be attached to these rings to support the middle of the bellows at full extension. (Unlike an accordion, which has one end strapped more or less firmly to the torso, in the Bandoneon/Chemnitzer, *both* ends are free to move, doubling the bellows extension possible for a given arm length. This is what necessitates the support frames for the one-third and two-third points in the bellows.
In the larger version of the photo, the springs (reaching from the left of each valve) are visible. They are screwed down to a wooden bar, and the other end rides in a groove in the back of the lever.
If you have already been through the pages on the English-made concertinas, you will see that this is very different in construction.
Here, we have the banks of reeds for the right-hand end. In the full-size image, you should be able to see the reed plates, the reeds, and the skins.
It is worth comparing the spacing of the blocks of reeds to the valve pads above. Each pad opens airflow to two banks of reeds.
Note that the reed plates are not waxed in place, as is common in accordions, but rather held in place by 'L'-shaped screws, against a soft seal material (chamois, or similar).
This is yet to be photographed. Keep your eyes open. (It really does exist, though.)