Luckily, I heard back from the chemist. The XRF spectrometer was in sight; able to bounce invisible light rays off my artifacts and reveal their precise chemical composition thanks to my old college friend Louise Kester.

Apparently paper is a simmering stew of organic compounds, or rather, an entire cuisine of varieties; each blend traceable to a specific moment. After Louise brought over the spectrometer for an evening of lo mein and x-rays, my IBM cards produced a compositional spectrum that was entirely unremarkable, but the compounds in the tea stain indicated Japanese origins and a high degree of carbon, which, I suspected—nay, had a genuine hunch—pointed to the roasted tea varietal of Hojicha.

The next day I drove to Arlington and rummaged through the local history archive at the public library in search of tea shops. Surely a tasteful Japanese green tea was not a common find in the supermarkets of the Seventies. I surrounded myself with stacks of old books, thinking how strange it was for historical publications to themselves become artifacts. A photograph of a shopkeeper and his son outside a Japanese market led me to Mikio Fukasawa, whose brief appearance in a 1976 newspaper article about his store led me to the address of Kenji Fukasawa, the boy who was now older than his mother was in the photo.

Impressively, Kenji had an encyclopedic memory of the years spent working in his father's store, and when I asked if he remembered any computer programmers from ARPA, he just about gave me a heart attack, “Oh sure. Mr. Matheson came by the shop every week. I always wondered what he did at work that made him drink so much tea.”

And so, Edwin Matheson.