What can you tell me about this graph; origin, data used etc?

Please note:  I am NOT questioning its authenticity; indeed, it appears in one of my old uni textbooks that was published around 1990.  

When it appears on THIS site, it is normally used to suggest something like, the current warming is nothing unusual, or that today's data has been tampered with, either to exaggerate the current warming, or to get rid of the Little Ice Age or Medieval Warm Period. 

Well, looking at the graph, the baseline appears to be temps around the start of the 20th century, with the final data point around 1970 or so. The start of the industrial revolution was around 0.25C lower, the coolest part of the LIA about 0.75C cooler, and the MWP around 0.75C warmer.  

So not too different to what we understand today, as far as I'm aware.  Would you agree?  

So what are the origins of the graph?   

On what data was it based?   

Was it a GLOBAL reconstruction?   

What would a modern graph, including data for the 50 or so years since then; What would that graph look like?   

Any other observations or comments?   

Thanks in anticipation ...