IWA 1638 System Wern ABC Circular Slide Rule

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Country of manufacture: Germany,       Date of manufacture: ____
Dimensions (length and width): 21.0 cm,          Weight: 87.3 gms
Materials: All plastic
Cursor: one piece plastic, front side only, 3 x 11.7 cm, one line + scale designations
Scales: 17
Front: 20 cm || M, N, D, A [ B [ T, S ] C [ r, P, a ] b [ U ] c [ V ] LL
Back: blank
Gauge Marks: [π ]
Condition: C0 (Mint condition)
Came with: Original black plastic case, instruction booklet, guide sheets
Notes: YouTube videos by Professor Joe Hernings explaining this unusual rule may be found here, and here.
Non-standard scale designations:
M (degrees) and N (radians) are used wirh the S and T scales for non-logarithmic trig determinations.
A, B, & C are equivalent to 8-decade versions of the standard D, CI, and C scales
D indicates the order of magnitude or decimal point
r, P, a, b, and c scales are equivalent to the standard K, A, D, CI, and C scales
U and V are used for percentage calculations
LL is a Log Log scale extending to 10⁴⁰!

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