Grading antique pieces

We discriminate 3 classes of pieces:

A-pieces: the real origin of the piece is known and can (theoreti-cally) be communicated to the client or to an honourable middle-man. The "fate" of the piece is known (who took it to whom, did anybody try to wash it etc.), too.
B-pieces: a first-hand source of intelligence about the origin is not available. More or less accurate "guesses" from experienced people. The "fate" of the piece is known - from the very moment when we got hold of it.
C-pieces: obtained from the trade. We propose the German expression „Strandgut“, debris that is left on the beach after a storm. Or we propose to compare it with a second hand car of unknown provenance, without papers, motor and chassis numbers are removed. Nothing is certain, the piece is "as is". We cannot take further responsibilities except for what we do (have done) with the piece.