Here is the User Manual for these models:
520-T-A2
https://www.sliderulemuseum.com/Pickett/Pickett_N520-T_USAF_AerialPhoto_GiftOfPhillipRodleyNZ.jpg
700-A2
https://www.sliderulemuseum.com/Pickett/Pickett_700_Type_A-1_USAF_AerialPhoto_SqBraces_TriangleLogo_GiftOfLeroyHauslerCollection.jpg