Regnier is describing the pre-production #26 made in 1899, which is a known piece and would be extremely valuable. Your friend is in posession of an early production example, either military or commercial, which is also very desirable and could be expensive depending on condition and originality, but it is a couple of orders of magnitude less rare and valuable than the one cited by Regnier.
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If it's made after 1918...it's a reproduction
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