Hi Larry,
The Durascale 100 made by MyWeigh has given me repeatable readings. You can Google for their website and link to online retailers.
The only calibrating tool I have for these is the manufacturer supplied weight.
Calibrating weights from two different MyWeigh models differed by some .08 grams for a 100 gram weight - a .08 percent consistency of the calibration "tool".
This weight variance seems good enough for our purposes, since we're concerned with repeatability more than we are with an absolute number. I don't think you care that my 1.87 is your 1.88 - especially since you need to work around the temperature in your room to establish your own norm.
Likely, a better calibrated 100 gram weight is readily available if this causes lost sleep.
The real challenge lies in measuring at record level, and here the price jumps considerably for a pre-configured solution. I'm working on having parts made for a small fitting to use with these Durascale 100's but will likely take a month or so before I get around to this.
The reason I'm using the Durascale 100 as opposed to the 50 is because the acrylic fitting comes in at about 75 grams and I need to be able to "Tare" this amount out.
Our mutual buddy Dmailer, builds up a platform to get the measuring surface of his scale to record level - without using a step-down fitting on the weighing surface.
This solution can likely work quite well with your Teres since your headshell is out in space. Pile stuff up under the scale by resting it on your tt shelf instead of on your platter. This could get a bit tricky with some 'tables. You'd definitely want this "stuff" you rest the scale on to be stable.
Cheers,
Thom @ Galibier