See above.My first impression was that it was a present someone had brought me from abroad. (It's an old diary) The shape, the lettering, the purple limp leather curling upwards at the corners, gave it a foreign look; and it had, I could see, gold edges. Of all the exhibits it was the only one that might have been expensive. I must have treasured it; why, then, could I not give it a context?
I don't get two sentence.
1. and it had, I could see, gold edges. = I could see that it had gold edges.
The edges of the covers were gold-coloured and I could see those edges.
2. why, then, could I not give it a context? Given that I had quite a lot of information about the diary, I couldn't understand why I couldn't work out where/who it came from.
and "I must have treasured it" is refer to value it or keep it?
To treasure something means to keep it and have great affection for it. If you treasure something, you are likely to keep it for a very long time, even after it has stopped having any use.