Lawrence Slide Rule 250-BT 1940s Vintage Engineering Instrument

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

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

Lawrence Slide Rule 250-BT 1940’s Vintage Lawrence Engineering Service w/Box

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

Vintage 10 inch SLIDE RULE Lawrence Engineering 250BT, in box with manual VG

Engineering Instruments Inc Slide Rule Vintage Ruler w/ Case Peru Indiana

Vintage Engineering Instruments Inc Peru Indiana Wood Slide Rule w/ Instructions