|Pair of Weston Master 715/S74's one with black and another with white display|
image by phollectormo (Image rights)
The Weston Master model 715 (US); S74 (UK) is a hand held light meter that started the Master series. This line has outlived multiple manufactures and finally ending with the Euro Master II in 2010. Sometimes these are referred to as Weston Master Universal because there is an alternate Weston Master Cine 720 model that only does cine, while the "Universal" can do both.
The earliest version are with black display has the word 'light' written across the top above the scale.
There is also a optimized version made for Bolex called the Bolexmeter. This version contains different measurement scales suitable for Bolex Cine cameras.
image by Anssi Puisto (Image rights)