1. Also known as the US Air Force Aerial Photo Slide Rule Type A-1.
2. Another example of a specialist rule made to order by Pickett.
3. This rule also came in a 5" version known as the Pickett 700.

Brand	Pickett
Model	520-T US Air Force Aerial Photo Slide Rule Type A-1
Country of Manufacture	USA
Scales Front	L, A, DF [CF, CIF, T, S, C] D, DI, K
Scales Back	Ground Size, Ground Speed [Image Size Centimeter, Image Size Feet, Focal Length] Altitude
Number of Scales	17
Slide Rule Materials	Aluminium
Cursor Materials	Metal/Plastic with Metal Screws
Cursor Lines	1 Front, 1 Rear
Scale Length	25 cm
Length	30.7 cm
Width	3.8 cm
Condition	Good, initials scratched on front left
Documentation	None
Accessories	Leather case