Concise Circular slide rule 28 English Version, made in Japan 1968

My Dad gave me this when I was in H.S. in 1968, I never used it (and neither, I doubt, will you) I've owned this for 58 years, so I'm listing it as USED however its in as-new condition with its original manual and packaging sleeve. 

・English specifications for “Slide Rule No. 27”
・This is the most popular circular slide rule, and it is a basic slide rule that can easily perform calculations other than addition and subtraction, such as multiplication, division, squaring, and cubing, so it is used in all fields.
・Types of calculations: General multiplication and division, proportionality (exponential percentages), squares, and cubes
・Back side: Unit conversions for length, area, volume, mass, temperature, pressure, speed, etc.
・Scale: D, C, CI, A, K (surface)
・Comes with a dedicated storage case and instruction manual.