Looks like this is the wide angle attachment for one of the Elgeet 13mm f1.5 camera lenses. Multi-element coated optics. Front barrel OD is 44mm and back threaded part is 29.7mm. Clear front element diameter is 26.6mm and rear element clear diameter is 16mm. The assembly gives a negative focal length of -31mm looking one way and -20mm looking the other way. If you need these for your vintage elgeet lenses, what a find! Or use them to experiment with. They look unused.