I thought that jmarkb would be the first to get this correct, and I'm glad that this has created some interest. The NLS maps are a great resource, but I still like to collect old paper maps. The one I took this information from was 1:25,000 first series sheet NT16 Balerno, which appears to have been first published in 1955, but my copy must be a reprint as the major roads have been revised 1971. So just 50 years old - incidentally the same age as our daughter who was born in 1971!
Oh, and I did do the calculation to make sure the map was correct.
I will have another completely different old map topic which I hope to put on this thread in a couple of days but please add your own contributions.
Keith