When your watch was new, it probably had #11 links on it. 511 is later, and there can be differences in vintage vs new examples.
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In this pic of my two 166.010 watches, the end links have a folded lip on the top "inside" of the end link. Later versions omit this lip. For that reason, if historical accuracy is your goal, then you want vintage #11.
For steel bracelets, don't be afraid to get it refinished if it's in crappy condition. Mine above was refinished, and the case gently touched up. I am a firm believer in "life's too short to wear a crappy-looking watch", but others seem to value the life it's led and the markings to show for it. Always up to you which path you want to take.
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