I need help in determining if these glasses are antique. If they are, what category are they (carnival, depression, opalescent, etc.). I could not locate any manufacturer stamps our markings. This set was donated at a thrift store I manage and no further history is available. It's a set of ten with the same pattern/design but in different colors (two are red, two are green, two are blue, two are amber). Also, can anyone suggest a potential value? Thanks in advance for your time and help.