This is a very rare tube and perhaps was made by Reeves around the 1850s or maybe slightly earlier. It is also a very rare paint being made with genuine Malachite. It will certainly be a long time before we encounter another. 
The paint here is soft and in my opinion quite useable. I have tried other tubes that came from this collection and found them to be very good with a good pigment load. Having said that it is a lovely antique in its own right and would make a worthy addition to any collection. 
As said I’ve used other tubes from this collection in my own art works and in my work as a museum’s conservator and found them to be good. 
The real benefit apart from the thrill of using a paint so old is that these paints have stood the test of time. Very many canvases in innumerable galleries must have oil paint on them made by the highly respected firm of Reeves.