8 Reales Cobs

My current primary scale came from ebay but you need to be very selective. Know what you want and keep looking until you find one that matches your needs EXACTLY.

Over the past 30 years I have had 4 mechanical scales of different levels of accuracy (three are still in good working condition - 3 beam, 4 beam and analytical balances and numerous digital versions. The only "broken" scale is one I got 15 years ago that had a spring dial. Those look convenient which is why I got one BUT the spring stretches and the scale is inherently inaccurate. I found it to be hard to adjust and temperature sensitive.

Digital scales are usually NO GOOD either because of inherent inaccuracies. Read the paperwork that comes with most scales and be prepared for a shock. I once saw a scale (electronic from China) that had a readout to 3 decimal places of a gram. Looked like 3 decimal places of accuracy. That's good RIGHT?

Well no - in the fine print it said accuracy guaranteed to 2% of weight. So on a 27 gram object that equates to a 0.54 gram a range or +/- HALF a GRAM. Digital scales to be accurate will set you back $500 at the least. Cheaper digital scales will simply not be reliable.

Mechanical scales have no parts that can go bad except the knife edge of the balance. They last as long as you do not abuse them.

Look for Ohaus type scales (school and college labratory types). They appear in sheriff sales too. Drug dealers use them so they can be really cheap at sheriff sales. Just check them out with standard weighs - make sure they zero and repeat each weight test 3 times.

http://www.ebay.com/itm/OHAUS-700-8...330893142735

This is a typical 1/10th gram scale - high school level scale - adequate for about 10% of fineness. This was the average standard level of accuracy in 1830 and was about as accurate as the Chinese schroffs were capable of determining. This effectively set the level of accuracy required for the Class 2 forgeries. A forgery above 800 fine will not be readily detected with this scale but coins that are debased lower than 800 fine will be recognizable.

http://www.ebay.com/itm/OHAUS-DIAL-...190814034011

That one is the dial type that I do not recommend. However the FREE arm feature is great for SG tests of coins. That is what this scale is made for. I just do not like the spring feature.


http://www.ebay.com/itm/Ohaus-Explo...300877998240

This a top of the line digital scale with the draft tight box required to get to 1/1000 g accuracy. But it is not set up for SG testing and you would need to devise an apparatus. NOT RECOMMENDED AT ALL.

The scale you really want that is good for all around work is one like:

http://www.ebay.com/itm/OHaus-Cent-...370779762283

This particular example NEEDS CALIBRATION - in other words you probably need to replace the knife edge because it is no longer accurate. So unless you are good at re-building mechanical things get a better one - but it is the best type. Accurate to 1/100 gram. That reduces the range of error to +/- 5/1000ths or plus or minus about 1.25% fineness. It will detect a debased coin that is 880 fine.

Here is the same scale new and under warranty.

http://www.ebay.com/itm/OHAUS-Cent-...290751031529

This is the type scale I use under normal circumstances - the accuracy is typical mint standard. If you can not detect a debased coin with this scale it meets mint standards.

I do not own a new analytical scale because I still do not trust digital. The older analytical Boxed scales are now classed as antiques. It is the type I used in college in 1966. I have not seen one for sale in 10 years or more.

But the Ohaus 311g is available all the time. It is a typical scale seen in Freshman labs in college.