The "Hint's to Tourists on The Lincoln Highway" guide mentions the various items to bring along for the Transcontinental trip. Most of the things are recognizable, like scissor (small), or a camera. Some items are less recognizable for their uses. A Rubber Sheet 6x7, yellow goggles, or "bachelor buttons?"

Bachelor Buttons, in this case, are buttons that use a stud pressed through the fabric and into a top button. They were sold extensively in the late 1800s and early 1900s as emergency buttons. There is a poem, "A Bachelor's Button," which is a lament by a man whose lover never sewed his button on his coat and had to use a bachelor's button to repair it. Haven't been able to find a copy of that poem.