Mike, my experience with used meters has been less thangood. Three of three have looked nice, functioned, and been in very rough agreement with my metered SLRs (three of 'em) at high noon. But in less than bright light, they've all been off.
The meter shops I've sent 'em to have found not so good problems with all three. Lunasix 2 to Empire. LunaPro (= Lunasix 3) to Bogen. And Master V to Quality Light Metric.
So my advice is to buy a meter that functions for as little as possible and budget for a trip to the shop.
Lunasixes, including the 3, offer incident and reflected metering. Weston Masters do reflected, require a diffuser (Invercone, in Weston-speak) to do incident. The first model of Invercone fits, IIRC, Master I, II, and III. The second model, IIRC, fits IV, V, and both Euromasters.
Another possibility the I remember fondly from the days of my youth when ... is the GR PR-3. Selenium cell like the Westons, has an incident adapter that's often been lost. But nice little meter.
Good luck, whatever you do don't look back,