Gerry, of all the double ended keys I’ve seen I haven’t seen anything like that one, very nice ! What sort of age is it and is the bow free to slide or is it fixed?
Simon, I’ve still got a small plastic crate full of double enders but its down to only the leftovers now and they are rusted to, well, you can guess what…
Did have a few nicely kept older examples with crisp wards and nicely turned flutes, bit like your smaller ones in photo 6, but most of what I have now are smaller castings I think from the 1920s or similar to yours in pic 5. Some of them are so roughly cast the wards are totally blocked by flashing, and quite a few of the larger ones had blowholes and noticeable flaws in the castings.
You have certainly set yourself up with an impressively mixed collection of all the different keys you have posted so far.