1. This mannheim professional rule is almost identical to the earlier model Acu-Math 511 (1) in my collection. The main differences are:
   • The later model has metal end pieces on both sides.
   • The cursor has cross-hatching on the plastic ends to allow for better grip
   • Model information has moved from each side of the front to the top of the front above the S scale.
   • The old model has drilled cutouts in the plastic to allow for grip. This has been removed for the later model.
   • Trig instructions have been added to the back of the slide.
   • New model is 3 mm shorter and wider.
   • Cursor is complete on both sides.
   
   
2. The Metal end piece on the left hand end of this rule and Acu-Math 511 (3) (Yellow) are both offset slightly, this corresponds with other examples I have seen.
3. This rule does not have the Acu-Math symbol on the right side of the middle bar, yet this is clearly seen on Acu-Math 511 - (3) (Yellow).

Brand	ACU-MATH
Model	No. 511 - Mannheim Professional
Country of Manufacture	USA
Scales Front	S, K, A [B, CI, C] D, L, T
Scales Back	Equivalents tables and Trig instructions
Number of Scales	9
Slide Rule Materials	Metal core, plastic faces with metal end pieces. Metal core looks like magnesium
Cursor Materials	Plastic
Cursor Lines	1 Front
Scale Length	25 cm
Length	31.4 cm
Width	4.2 cm
Condition	Fair. Missing a rivet head on front left. Former owners name written on back.
Documentation	None
Accessories	None