1900 No H Large Cent Underweight + Questionable

Your coin is a 1900 and not an H. The mintmark is at the bottom between the leaf and the denticles. Your 1900 plain coin is a little harder to find than the H's, but still not scarce enough to have someone fake it. Take another large cent and put it on the same scale and see what it reads. What was your weight when you got the .11?

Obviously you are a new collector. DO NOT buy shiny cents that have wear or marks all over. Any copper coin below AU will not be all shiny with even colour. That coin was not only cleaned, it was POLISHED to death ! I have used BRASSO to see what it does to rusted cents and it looks exactly like that. You can see that there was rust under the date; it was probably so heavily polished to get the rust off that it lost weight. Sorry but it has lost all numismatic value, and is only good as a filler or decoration.
A polished coin looks almost gold-coloured and has a matte (dull) finish. A dipped cent (dipped in silver cleaner) looks orange, all over. A real uncleaned shiny cent will have a slightly red tinge with a different look at various angles, like the one below.

In my experience, 5.55 grams is well within tolerance for The Royal Mint, even for a mint state coin. One-cent coins were token coins, with the intrinsic metal worth much less than face value. The mint used much less care getting the planchets to the correct weight than they did for the silver and gold coins.