I have two C/G Anglos.
My Morse Ceili (all wood, accordion reeds) weighs 2 lbs 1.7oz (954g). My Kensington (metal ends, traditional reeds) weighs 3 lbs 2.5oz (1.43kg)
The difference is pronounced. I think the Morse must be one of the lightest concertinas there is, and, needless to say, it's way more comfortable to play standing up. I don't have particularly robust wrists, and sometimes that difference really matters to me. In the situations where I want to play standing up, I don't think that a neck/shoulder strap is very desirable for me. I improvised one once (for another larger box) and I didn't think it was great. One of the reasons I still have the Morse is because it weighs so much less.
On the other hand, I agree with the builder of the Kensington that it's a feature, rather than a bug, of the that instrument's design that it is built very solidly and has end frames of a composite material that I think is probably heavier than typical concertina woods, but which is super-stable and durable (and I suppose may have desirable sonic properties as well, as it's very hard and therefore probably absorbs little energy). I play the Kensington a lot more. It sounds better to me for most of the music I play.
I would be curious to learn about the weights of other 30 button C/G Anglos, for comparison. Is my Kensington heavier than a vintage box? By how much?
Some knowledge of weights might inform future purchases - and then again it might not, since the sound, reed response, button and bellows action, and (for better or worse) price will probably always be more important.