https://www.ebay.com/itm/1971-Beach-Boys-Dennis-Wilson-hand-written-note-to-Dad-I-Owe-You-50-cash/143730306492?hash=item2176fe6dbc:g:ExYAAOSwUyZfWkzwRockaway Records which often sells curious memorabilia on Ebay and its own site has come up with a dilly this time: a note in longhand from Dennis agreeing to repay a $50 loan from “Dad” at Bri-Mur publishing, as an advance for “See Spot Run Prod. Co.”
Mountvernonandfairway.de in its miscellaneous topics page lists the five songs published by Bri-Mur: "Break Away," "Soulful Old Man Sunshine," "Shyin' Away" and two Dennis songs from 1971, "Behold the Night" and "It's New Day." The document is dated 1971 and the handwriting is quite recognizably Dennis’ so it looks authentic... but what See Spot Run was and how it connected to Dennis’ songwriting at that point I don’t know.