Bertoia bench, Knoll 400  

Hi there,
two weeks ago I've bought a nice black bench (in Germany) and I think it is an old Bertoia bench. Sadly it was painted black, but only on the top. With a help of a carpenter we've took out the rusty screws (a few broke..) and renovated carfully the slates. In the end we've revarnished them with a few layers of shellac and polished them with wax.
The slates are more or less 160 cm. All the benches that I know have only four screws per slate but mine has eight. Is it not original or maybe a very old version from 1952? The bench has no label but the slates are numbered with stamped roman numbers from I - VIII.
Thank you for any advice!
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