10" Engineering Instruments Slide Rule Model 250-BT W/ Case

Vintage Engineering Instruments 10” Slide Ruler Model 250 -V

Vintage Pickett Student Slide Rule w/Case and Instructions, Apollo Edition

Slide Rule - Engineering Instruments, Inc. 250-V w/case & instructions

Vintage 10 Inch Slide Rule Engineering Instruments - Model 250 BT Peru Indiana

Plastic Face 10 Inch Measuring Slide Rule Model 250-V Engineering Instrument

Vintage 10 Inch Slide Rule Engineering Instruments - Model 250 BT Peru Indiana

Vtg Engineering Instruments Inc 10" Slide Rule 250-V W/Box/Case/Instruction Book