The main importer in turn reacted by numbering each sold instrument and engraving it visible from the outside. This number suggested to be a serial number being at the same time the proof of the original instrument. Not numbered bandoneons were then considered not original being less considered. On the second hand market false numbers were then common. However with some routine they may well be recognized
Inside the instrument you'll find in most cases a hand written numbers, later they where stamped. These numbers again are not real serial numbers. They were used during production to keep parts of one instrument together. You may find them on reed boards or on the bellow frame. The bass side with a B prefix, the treble a D (Diskant) In fact, the numbers were not current. They are not related to any production year or about the number of produced instruments. Many instruments were exported as kits to be assembled at destiny, a way to circumvent the high taxes applied to ready-to-use bandoneons.