Hi Phil,
Even those tunings that have official titles can vary by quite a bit. Some players liked to experiment with their tunings so that the flatness of one reed isn't equal to the sharpness of the other etc.
Andre Verchuren's tuner used to be bombarded with requests from people, amateurs and pros alike, asking for their boxes to be tuned the same. Now, he had access to Verchuren's accordions and was able to make note of what each reed was tuned at. He frankly admitted that even after many years of trying he was unable to replicate the sound of Verchuren's accordion exactly. Even when he was presented with exactly the same box model and the same reeds it just wasn't possible.
There is obviously scope to consider he was paid handsomely to ensure that he never made a facsimile of Verchuren's accordion, but I suppose only a very few people will know if that was indeed the case. Verchuren's son, Harry Williams, played a box identical to his father's, with the only difference being that it was a C system and his father's was B system.
I would wager that both boxes were tuned identically, but the fact was Harry Williams wasn't possessed of the same technique as his father, and the boxes sounded different. I therefore share the view with other members that tuning is one thing, but producing the sound is another. Bellows expression and control, together with the style of attack of the right hand, can have a major effect on the sound of the same instrument, and it is often the case that one player sounds different to another on the very same accordion.
I lived in Edinburgh for some years where there was a sizeable Italian community, and the minority of Italian accordionists who played CBA preferred a lighter musette to the typical Scottish tuning. To that extent quite a few Paolo Soprani Internazionale CBA models used to circulate in the Edinburgh music shops, but the Scottish players didn't like them, as the musette wasn't strong enough, and the treble buttons were all white instead of the usual black and white bicolour found on Scottish CBAs. Consequently, they were a bit cheaper than the equivalent Scottish tuned boxes of the same make, and if I had been a bit more "accordion wise" at the time my house would have been full of them, instead of the French boxes I ended up buying. French musette on an Italian accordion shouldn't really be an issue for we non-French types, but I was image conscious in those days. The Sopranis came in any shade of black or pearloid red, but they were probably the best all round LMMM CBA accordions available in Scotland at the time, for those of us who didn't play in the Scottish style.
Hindsight is one of the greatest tools the world has ever seen, and it's just a pity we can't take advantage of it 30 odd years before it becomes useful.
I'd say that you have a winner with the Hohner and don't be in too much of a hurry to rush into anything else yet.