TestLab Digital Multimeterzzz range electronic digital multimeter model KD- 4200. The circuit incorporates two field effect transistors and has an input resistance 10 megohms on DC voltage ranges. It requires one 9 volt PP3 type battery. Working, Korea and Japan, date 1989/90.
This is one of several instruments given to me by Deborah Waters, which belonged to her late father. It has required no attention other than cleaning, and replacing the battery.
Back of the instrument [note incorrect battery details]
Internal view [note date code on integrated circuit]