You seem to be describing a Mexican Pillar coin - unknown denomination. However, before you go much further you need to be warned that 1756 is a heavily counterfeited date and some are made with silver. A picture of a real coin will do you NO GOOD. You are not familiar with the type based on your description so a picture is not adequate.
Please post clear pictures of your coin and we can help out with the identification.
Please post clear pictures of your coin and we can help out with the identification.


















