A collection tells you what somebody learned to distinguish from the ordinary background.

Collecting is mostly a training in noticing. Before the first item they all looked the same; after a few years, someone can see difference where other people see a heap, and the shelf records that education rather than the buying. The objects are evidence of an attention that got finer. Which is why hearing an enthusiast explain their categories is more interesting than looking at the collection.

When someone shows you what they collect, ask what makes one of them better than another. You will learn more in five minutes than from any amount of polite admiration. And notice what you have quietly learned to tell apart yourself.