![File:Vintage Accurate Tube Tester, Model 257, Accurate Instrument Company, Made In USA, Circa 1968 (32890802281).jpg - Wikimedia Commons File:Vintage Accurate Tube Tester, Model 257, Accurate Instrument Company, Made In USA, Circa 1968 (32890802281).jpg - Wikimedia Commons](https://upload.wikimedia.org/wikipedia/commons/thumb/5/57/Vintage_Accurate_Tube_Tester%2C_Model_257%2C_Accurate_Instrument_Company%2C_Made_In_USA%2C_Circa_1968_%2832890802281%29.jpg/2560px-Vintage_Accurate_Tube_Tester%2C_Model_257%2C_Accurate_Instrument_Company%2C_Made_In_USA%2C_Circa_1968_%2832890802281%29.jpg)
File:Vintage Accurate Tube Tester, Model 257, Accurate Instrument Company, Made In USA, Circa 1968 (32890802281).jpg - Wikimedia Commons
Accurate Instrument - 157 - Tube Tester - Schematic (1963-04-11) : Accurate Instrument : Free Download, Borrow, and Streaming : Internet Archive
![MZE-Electroarts Entertainment - MZEntertainment.com: Accurate Instrument Co. Model 257 Tube Tester with Dr. ZEE WORKSHOP Custom Wood Enclosure Case. MZE-Electroarts Entertainment - MZEntertainment.com: Accurate Instrument Co. Model 257 Tube Tester with Dr. ZEE WORKSHOP Custom Wood Enclosure Case.](https://www.mzentertainment.com/pics/test_equipment/acurate_instrument_257_tube_tester/accurate_instrument_co_inc_model_257_tube_tester_schematics.gif)