The green version is a later design, patented (see links page) by a Walter Georger Batt. This features four removable red glasses, covered by "shields". One "shield" has a movable disc (not mentioned in the patent) which uncovers a hole that aligns with a clear circle in the corresponding glass. Once lit this allows the lamp to emit, in addition to red light , a small pencil beam of white light upwards. The purpose of this is unkown, at this time, but may have provided a method of illumination to alllow I.D. cards to be viewed or somesuch.