is the literal translation. There is too little context presented, I'm afraid. If 'leather clothing' is meant here as I suspect and as it's implied by the previous context, then it could be either 'surtannage level/(grade)' or 'resin tannage level/(grade)'. Perhaps both. The choice is yours. Hope it helps. Good luck, Helene!
Re.: Oxford Engelsk-Norsk Ordbook (Hornby, Svenkerud) ISBN 82-02-02257, + 1. Russian-English Polytechnic Dictionary (About 90 000 entries), Moscow, Russian Language Publishers, 1982 + own experience

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Note added at 2003-10-31 08:43:56 (GMT) Post-grading
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Takk & thanx, Helene!