The appraisal of a string instrument requires that the instrument be physically present at the time of the appraisal. This is not a feat which can be accomplished over the internet. Many factors are involved in the determination of the value and origin of a violin, viola, cello, bass or bow.
Labels appearing inside of instruments can be extremely misleading.
Likewise, on many occasions certificates can be either misleading of downright false. Some labels have been inserted into an instrument to deceive while others are inserted to inform the observer of the model after which the particular instrument was fashioned. Certificates can be falsified or even counterfeited. The process of appraisal also must take into account the overall condition of an instrument with regard to cracks, replacement wood or patches in the actual body of the instrument, parts which may have been added later such as a neck, a rib or a top or back, thus making the instrument a composite. The level of craftsmanship is also an important factor in determining origin and value.