Notes: "This is a pre-1950 Hemmi model 2664 slide rule with a scale set that would be called a Rietz, or almost a Rietz. I have seen this model referred to as a business slide rule, probably because of the CF and DF scales. However, with four trig scales that give tangents from 6 degrees to 76 degrees, and sines from 35 minutes of arc to 90 degrees – note that to three significant digits, i.e., slide rule accuracy, the sine scale for 35 minutes to 6 degrees is also a tangent scale – it is quite a useful engineering slide rule. Curiously the A and L scales share the space of one scale, with the left half being the A scale and the right half being the L scale. Later models (post-1949) featured full-length A and L scales, but lost the small-angle sine scale. "
