Information from the sales catalogue:

Original leaf from a medieval manuscript Breviary. Ruled for 27 lines of Latin text, written in double columns with dark brown & red ink in fine rounded gothic book hand on animal vellum. One elaborate five-line illuminated initial in red with white penwork, outlined internally in gold with further internal floral design -all sitting on a burnished gold ground & extending into the margin with red with intricate penwork & burnished gold bezants. The unusual lower margin is illuminated with an orange vase in the center, two floral designs on either side in red, blue, green and gold surrounded by intricate penwork and gold bezants! Nine two-line illuminated initials alternating in red with delicate violet penwork and blue with delicate red penwork - all extending in to the margins.
Northern Italy (Padua?), c. 1460.
The elaborate illuminated "D" (recto) begins the Proper of the Saints for 29 November:
"Deus qui nos beati saturnine martyris..." (O God, as you allow us to rejoice in the feast of your blessed martyr Saturninus, grant that we may be helped by his merits)
A Breviary is composed of many books (prayers, hymns, psalms...) painstakingly but carefully written by hand, & used by monks & priests to conduct daily services.

The elaborate decoration on the recto is undoubtedly due to it being the first leaf of the proper of the saints.

Northern Italy? Padua?https://sdbm.library.upenn.edu/entries/39917

Purchased from Charles Edwin Puckett, Akron, Ohio

Possibly from the 449-leaf breviary listed in Reiss & Sohn, Wertvolle Bücher, Landkarten, Ansichten, Auktion 91:II (2003, October 21), lot 503 (SDBM 39917). In turn, this was likely the same codex as SDBM_MS_2190, listed in Dorine Proske-van Heerdt, Fine Medieval Books in 1994 as a ca. 1450, 446 leaf breviary, which itself was listed as Lot 24 at Sotheby's, Mediaeval manuscripts and miniatures, 2 July 1951.