A well made ivory parallel rule retailed by Otto Boettger in Adelaide and so marked. Boettger arrived in Adelaide in the mid 1870's and set up as a scientific optician and instrument maker with a retail shop. He also had a thriving business as a reseller of imported instruments and scientific tools. He was highly regarded as an instrument maker. He returned to Germany in 1899 after selling the business to Mr G. C. Kohler who had been his apprentice. The business continued to trade under the name of Otto Boettger.
The ruler is marked "ENGLISH MAKE". It pre-dates the Mc Kinley country of origin markings which would date it prior to 1890.
Nickel hinges and finger pieces.
Very good original condition.