Thinking of buying a microbalance online? With so many people now a days selling just about whatever they find from auctions, estate sale, garage sale, thrift store, flea markets, stolen goods, close outs, etc.  not everyone know what they are buying and selling online. This combination generally creates a problem, as a buyer, you don't know what you're going to get;  and it's more of a problem when dealing with a highly specialized thing like a microbalance.
A microbalance is a scale, a weighing  equipment generally used in a lab or  production environment. The  main characteristic that make a microbalance different from other scales , is that a microbalance can weigh down to a 0.1  to 1 microgram. That's 1 millionth part of a gram( there's about 27 grams to an once). These are precise equipment that requires proper handling during initial setup, calibration and during use ( weighing). The most common damage to these delicate instrument occurs while being transported improperly. It's important to follow manufacturers instructions normally outlined in the users manuals. An improperly handled instrument can be damaged and the person not know about it. A
The cost to repair these instruments can be very costly. That's where a potential buyer needs to make sure the balance is tested and handled properly.
Some points to keep in mind when looking for a microbalance.
1. Is it complete? Normally instruments may comes with other parts like accessories, cables, manuals, weights, softwares, etc.
2. Is it known to work? Repairs can be costly. Factor the high cost of repairing an instrument and it's shipping to a service center.
3. Have an assurance from the seller that the unit is working when you get it, again the cost of repairs and shipping can be high. have it shipped properly from the manufacturers instructions. It's important to follow the manufacturer's procedures for shipping, setup, use, etc.
4. Is the unit an older unit that does not have support( service and parts) from the manufacturer?
5. When was it last calibrated? Some requires calibration  that has to be done to certify the balance is ok.
One last point- a microbalance has a specific purpose and it has to work properly- usually the unit has to certified that it is working properly t work or appear to work). Data produced from these instruments can affect us in the end.

I guess the above is pretty common sense and it can apply for may things in general. So enjoy bidding and good luck.