Lot of 21 White Instruments 3900 Filters Various Hertz LIC U.S. Pat 3,256,391
The patent number, LIC U.S. Pat 3,256,391, adds to the value and rarity of this item. List of filters (hz).
The patent number, LIC U.S. Pat 3,256,391, adds to the value and rarity of this item. List of filters (hz).