I have probably had these two matchbox sizes light meters for over 30 years. They were a common find in second hand and antique shops and fairly cheap back in the 80’s. My guess is the design dates back to the 60’s.
The one on the right looks far more complicated but it is displays the same information as the one on the left. I used to use them but they require a little more thought and time than an in camera meter.
Out of respect I used my Calcuflash incident light meter to set the exposure for this image. I bought it back in the 80’s too and you can still buy them today.