A couple of details about my new bandoneon. The metal plate over the main valve carries the brand name "Tango"; Oscar Zucchi's description suggests that it was produced by M. Hohner. However the cover is typical of ELAs and many other detail suggests that it was indeed produced by Ernst Louis Arnold. As Christian Mensing explains, these brands were originally produced by ELA, distributing them through M. Hohner was only part of ELA's marketing strategy. I also got in touch with Hohner and Christian Baumann kindly confirmed that this bandoneon was not made by them. So since both Ben Bogart and the original owner say they are sure it's an ELA, and it looks and sounds like one, I'm quite sure it is. According to the previous owner, who bought it in a bandoneon shop in 1999, it was produced in 1936. Here is a picture:
and another photo of the cover:
Some basics: it is a 142 tone bisonoric concertina. I was quite happy to notice that the reed plates are made of zinc, not aluminium, which are widely considered to yield better sound quality. Although scratches on the reeds show that it was tuned a couple of times, it's in a pretty good condition and probably wasn't used by professional musicians. I venture this because it still has the original tuning of the factory, meaning that three rarely used keys on the bass side play notes differing from the standard tango tuning. (I forgot which three and what is the difference.) A serial number is written inside with a pencil, it reads 35587.
The reeds are covered by plastic instead of leather, but this is a minor issue, as far as I know it will only affect how frequently the reeds need to be cleaned. The bellow has few small holes but the leak through them is fairly minimal. The main valve has a more serious problem, it yields too easily when you try to force the instrument to open without holding down any of the buttons. On the long run this needs to be fixed, but it's not a big issue, and I hope that cleaning the leather on the main valve - which seems pretty dirty - will take care of it. Another minor problem is a crack running through the half of one of the mounting boards. Aesthetically it's in a pretty good shape: one of the pearls is missing, the lyra in one of the corners is damaged, and there are few other signs of wear and use on the paint under both handles, but otherwise it looks as new.
Couple of other photos from the inside: