An exceptional silver grade MK in Triangle; congrats on adding this beauty to your collection.
To date, it is accepted these ISA's were produced in the Gabloz area but, we still do not know who the actual maker(s) are.
Some theorize the MK stands for “Metall und Kunststoff” and the Triangle represents a grouping of manufacturers.
Hopefully, someone will find solid proof on actually produced the MK in Triangle.
Best regards, fischer
This is found in Gablonz
that's a beauty.