If you haven't been over to Scription, you should start by checking out this posting about Field Notes co-founder Aaron Draplin and his collection of vintage memo books, the inspiration for what is now Field Notes.
Aaron has a very large collection of these (primarily agricultural) notebooks, and they just look awesome.
While looking through an antique store today, I happened to come across this little memo book, a notebook provided to a Mr. James L. Olson by KX Hybrid Seed Corn, a brand under the Northrup, King & Co.
A little extra digging revealed that the Northrup King Building is a historic site that is now used as a creative arts center and entrepreneurial hub.
As for the agricultural memo books, these memo books often contained reference pages to assist farmers in increasing crop yields, measuring grain, and providing information on how to best utilize their land under a variety of weather conditions.
\The notes I jot down may not be critical to my livelihood, but it's always nice to have paper handy to take down a recipe, book recommendation, craft ale tasting notes, or maybe even a Zentangle. Regardless of what needs to be recorded, I cannot imagine life without my memo books. Having an external system complements/supports internal thought and is key to productivity, efficiency and, ultimately, my happiness.
What brand, format, or style of paper do you carry with you at all times?