Hello All
My opinion of the ISA is it belongs to the Vienna Design family of ISA's and is attributed to the firm of Wilhelm Hobacher.
The Vienna firms of F. Orth, GR&Co and R. Souval all share the same obverse design as the Hobacher.
Your example has the block hinge hardware...there is another mm W.H. that has a sheet metal hinge also.
Best Regards, fischer
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