James Newmans business stretches all the way back to 1784 and he was a fine fine maker of almost anything required for the artist. The business at Soho square was established in 1801. 
He was especially noted for the quality of his colours. In 1811 he was singled out by John Burgess an influential artist and author of a book on painting. This was called a practical treatise on the art of flower painting. Mr Burgess actually listed three colourmen but stated that Mr Newmans colours were pre eminent. He was especially noted for the quality of his Indian Yellow amongst others. 
It seems that many others agreed and Newmans were in business for the better part of 175 years!
It has taken a while for many people to share my passion for Mr Newmans offerings but this has recently changed with a bit of a vengeance! Boxes by him now sell astonishingly well and of course prices for such things will soar. 
This particular box was I believe made around 1850 and in my estimation is a fine example. 
It is also really rather rare in that it is a thumb hole box. 
These are rare by any maker but one by Mr Newman is in my experience exceptional. This one is made rarer still in that it has all but four, I believe of its Newman pans. Many of these are full pans and most have there original colours. All of the pans here are ceramic and so will last virtually forever. 
In my forty years of collecting I’ve never seen more than about five of these pans by Mr Newman in the same place. Other people may have done but I’m quite sure that it is rare to find so many together. As to why I can’t say for sure but I imagine that such things have been sought after for the quality of the colours.
The box is generally in good condition. Not at all rusted out and strong. It has a few shallow dents from use as might be expected and of course some paint loss but nothing that will stop it working wonderfully just as it always has. 
It opens and closes just fine and the hinges are good. 
I’ve also tried one or two of the colours and they work well. 
With a thin coat of clear wax on its inner surfaces this box will easily do another hundred years or more of work just so long as it’s looked after. By this I mean keep it dry and it can’t rust but I’m guessing you already know that!
The clear wax works very well though as it prevents water from penetrating it and all the boxes I use have wax applied. 
Being a thumb hole box makes these boxes easier to use than the ones with rings in my opinion. The conventional palette which evolved over a very long time also uses the thumb hole. I’m sure that this is for the fact that it works very well. 
This is a box of ample proportions but to me at least it is not heavy. Those large mixing areas are very nice to use with plenty of space and to be honest it’s not easy to go back to the smaller ones!
All in all this is a lovely box and really quite rare. For this reason in my opinion it is a good investment also. Being a joy to use is also a kind of an investment in whoever is lucky enough to work with it.