First of all the lightmeter is an essential piece of kit for the serious photographer.
Why use a lightmeter anyway? my camera works well on auto & programme. Your camera measures light being reflected from the scene, meter from the brides white dress for a high level reading & the grooms black or dark suit for a lower reading, I rest my case. To make a meaningful light reading you should be measuring the incident light, that is the light falling on the scene. In digital & high quality traditional chemical photography your are measuring light in 1/3rd of a stop increments. This is were I advise using a new or certainly not an ancient lightmeter for such a precision job.
In storage & use for many years the photocell deteriorates due to various forms of chemical action, even when kept in the dark, quite frankly you would not buy other old chemicals, and that is what your a doing with an old lightmeter, even if the chemical is encapsulated in the device. The are also issues surrounding battery availability with some meters, using the wrong but 'near enough cos it fits' battery will in most cases render the calibration to be inaccurate. For serious use do not consider a meter much over 5 years old, unless it has been serviced & recalibrated.
If you are collector of older light meters a an object d' art or just for fun ignore the above, the guide is for the serious user of these precision instruments.
O yes, I am a professional photographer of some 25 years in the business.
I hope this helps