Can I determine the year of manufacture of Olympus speakers given the speaker serial numbers 46499 and 46500. I am going to sell a set and want to provide proper information. The speakers have a single bass and two lenses above. Thru one lens I can see the bullet tweeter (075 ring radiator?), but I can only see a horn mouth thru the other lens. Is there a way to positively determine it is a 375? Since these cabinets predate the passive radiator, is that a means of determining the year of manufacture? Is there an easy way I can upload a photo of this system for your analysis? Thanks from a Newbie (first post).