Hi, Everyone!
       Thanks for the info on calipers.

       Now I have a new problem - how can I get rust off a small shell.  Some exhibits ago, I mounted some miniatures on pins to make them more visible.  Unfortunately, some of the pins rusted.  I have a golden yellow Stomatolina rubra (Lamarck, 1822) that I want to mrescue!

                        Thanks again,
                                Linda