I use a Weston Master III that I bought of the 'bay for pennies, and it's readings tally fairly closely (say, +/- a stop difference max) to those of my Weston Master IV (that recently had a new cell fitted) and my Nikon F2 photomic.
The only real issue is, as Phototone says - the lack of sensitivity in low light. The Weston IV. V and Euromaster's are a bit better than the earlier models in this respect, but no selenium meter is ever going to be ideal for these situations.
If you mainly shoot B&W or C41 colour, unless your meter is miles out, you'll probably be fine.
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