The numbers stamped on the frames refer to the model number
designated by the frame manufacturer, as well you will find some
other numbers referring to the size of the frame.
For example, looking at my husband’s OGI frame the number’s listed
on it are MOD 2191 for model 2191…Then 43 20 for the eye
size,Then 135 for the temple length. This really isn’t very
useful for you. However, if you know who the manufacturer
is, in this case OGI, and the model number you may be able to find
the frame on line and look up the material. Good Luck!