VERY RARE 1937 VINTAGE NATIONAL RADIO CO. MODEL CRM CATHODE-RAY OSCILLOSCOPE. The little National CRM oscilloscope with its one-inch wide CRT screen was introduced in 1937. It is based upon the RCA 913 oscilloscope tube which looks like a metal 6L6 with white glass at the very top. National designed this very small and simple scope around that tube. There are no amplifiers in the scope. The only other tube in the scope is a metal 6X5 used as a half wave rectifier. Its horizontal sweep which can be switched off is derived from 60Hz from the power transformer. Photos are the actual National model CRM Oscilloscope In good condition. Scope has good display. Almost every older electronic item will benefit from a careful alignment and cleaning or other restoration. Image may not be unique. I do not divulge reserve prices. Please contact me directly for any further information. Powered by SixBit’s eCommerce Solution. The item “VERY RARE 1937 VINTAGE NATIONAL RADIO CO. MODEL CRM CATHODE-RAY OSCILLOSCOPE” is in sale since Tuesday, August 04, 2015. This item is in the category “Consumer Electronics\Radio Communication\Ham, Amateur Radio\Other Ham Radio Equipment”. The seller is “radiotyke” and is located in Greer, South Carolina. This item can be shipped to North, South, or Latin America, to all countries in Europe, to all countries in continental Asia, to Australia.