Why clocks in shop always 10:10?

This is the unaware question puzzled me by my sister years ago. By that time, my sister told me, after she searched around from her friends, saying 10 past 10 will exactly showing a smiley-face, which welcomes the customers of the time-piece shop.

Last week, i'd been visited a watch repairing specialist, highly recommended by my colleague. We chat a lot while i'm looking on the best piece to suit my favor and my wallet. And suddenly he asked me if knowing why clocks or watches always showing 10:10. Of course "smiley face" was my answer proudly. But he turned me down... and told me that, 10:10 is the exact time that the first watch in the world to be born.

Of course, there're few more versions as the answer for this query.

I'm not sure how true is this information still. Hope anyone out there can give some comment.