The BM mark (Business Machine) can be found on the label and manuals
This mark was issued by the Japan Business Machine Makers Association (JBMMA) in 1974 when the export volume of calculators passed the mark of 10 millions units.
These two articles in japanese: Establishment of quality certification system for calculators and Calculator Quality Certification System (BM Mark) give some explanations about the mark. These articles can be roughfly translated and resumed by:
The calculator quality certification system was established in March 1974 by 14 member companies of the calculator subcommittee after a two-year preparation period. It was established with the aim of supplying calculators that users can use with peace of mind by preventing deterioration in quality, performance, and after-sales service that tends to occur due to excessive competition in the calculator industry.
This french advert give some additional information:
"Answers always accurate with BM mark calculators."
"An electronic calculator with BM mark is defined by his excellent quality.
The companies part of the Association are the following:
The mark can also be found on some non japanese brands (but made in Japan):