Key Word

I was wandering through Edinburgh's streets when I spotted these intriguingly old keys through a store window. I tried to go in, but the owner said he'd closed for the day. Dismayed, I stayed by the window, marveling at their shapes and sizes. Soon, he stepped out to leave, and I asked him when he'd be open again. After being momentarily vague he asked me what I was interested in. I mentioned the keys. He was immediately thrilled and let me in, while leaving the closed sign on. I took my time picking archaically intricate keys while he regaled me with key stories.
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I guess, I knew the 'key' word.