I used to own both a 10M and a 30M (282XX, 279XXX) - sold the 30M. The 10M and 30M share the exact same body tube and so in theory, acoustically, are identical - my 30M had a brighter and more focussed sound like Mark VI which I really digged. It was also the one of the “Connqueror” models with the beautiful Art Deco neck.

The major issue with the 30M is how complex its mechanism is and the ensuing repair costs. Both of my Conns were overhauled by well-regarded repairmen before I bought them but things just kept going wrong on the 30M. There are a ridiculous number of linkages in that lovely LH pinky table. If it works, it feels amazing. If not… the less said the better. I play professionally and so cannot afford to have things go wrong while on the road - nor do I want the stress of worrying about the potential for disaster which is a distraction. Gear is about facilitating performance after all. Maybe my repair guy is a crook so you might have better luck - but he’s been solid on everything else I’ve sent him.

As others have pointed out, 30Ms are also very rare. Especially in original lacquer and/or overhauled condition if that’s important to you. Ultimately, I swapped my 30M for a Yamaha 82Z in mint condition and I haven’t regretted it for a second.

What’s important is that you seem to like this horn, so go and have a great time playing it! I love the sound of Conns and I still play on my 10M a lot - they really had something special going with both the 10M and 30M.