Vintage 1940s Keuffer & Esser Co NY slide ruler leather case 13” marked drafting

Vintage 1940s era Keuffel & Esser drafting slide ruler with leather case. Case has Bucknell banner sticker, along with two others that look like Purdue ? On the back. Name stamped on case front is Dave Schaffer. Same name is also engraved on metal piece in slide ruler. Marked Keuffer & Esser with patent numbers. Last photo shows a single crack to plastic clear piece. It does not affect sight to numbers, functionality or appearance. I’m very good to excellent vintage condition. Case measures approximately 13” long x 2.5”W, ruler measures approximately 12.5” long x 2”w.