UH0890. See The Morgan Library and Museum’s image of the watermark found in the paper Caterina Sforza used to write and lock a letter in 1477.
Unlocking History number (UH#)
UH0890
Original
“Caterina Sforza to Ludovico Sforza (December 18, 1477) mentioning that a majordomo of Caterina Sforza's husband, Girolamo Riario, is sent to Ludovico to inform him about the well-being of Caterina's husband and the trust he can place in her person,” Unbound Ser. 2 MA 2691.012 (Corsair, The Morgan Library and Museum online catalog).
Model and research notes
MIT Libraries, Unlocking History Research Group archive, MC0760, Box 54.
Letterlocking Unique Video number(s) (LUV #s) & Instructional video(s) URL
Forthcoming
Instructional video info transcription
Forthcoming
Letterlocking Category number (LC #)
LC15L
Letterlocking Format number (LF #)
4RW
Security score
Low
Assessment of Confidence in assigning LC#
Attested
Substrate
Paper
Dimensions
Opened (in mm): H: 199mm x W: 214mm
Letterpacket (in mm): H: 75mm x W: 85mm
Manifestation
Opened
Distinctive letterlocking style(s)
Holograph letter
Locking mechanism
Lock
Security enhancements
Authenticated covered seal
Letterlocking category formula (shorthand)
LC15
Fold + Slit/Hole + Adhere + Lock-O
(F + S/H + A + LO)
Letterlocking manipulation sequence (shorthand)
Fold + fold + fold + fold + slit/hole + lock-O + adhere
Locking instructions
Edge fold at the left edge to function as a margin fold. Unfold. Write and sign the letter. C-fold top and bottom edges toward the center. The top and center panels are equal. The bottom panel is slightly shorter. Keep folded. C-fold left to right edges towards the center. The left and center panels are equal. The right panel is slightly shorter. Keep folded. Slit made parallel with the left and right edges of the letterpacket passed through all the panels of the folded letter. Create a shaped paper lock-O from a paper remnant with a pointed tip that passes through the slit, wrapping around the right edge. Seal the letter by applying warm sealing wax over the lock tip and sandwiching the lock tip between the letterpacket and the broader side of the lock. Create an authenticated covered seal by impressing the seal-stamp into the sealing wax through the paper lock.
Images
Foldable(s)
Forthcoming
Step-by-steps
Forthcoming
Substrate map
Forthcoming
Virtual unfolding results
NA
Manipulations
Writing: Margin fold
Postal: NA
Opening: Tears
Filing (Storage, Display): NA
Repair: NA
Damage
Edge tears and folds at the right edge
Features
Dirt on panels/ in crease
Bird watermark: one in the lettersheet, one in the lock. (Briquet 12147; Rome 1481)
Exposed seal design: the coat of arms of the Riario-Sforza family with a dragon, a rose and the empty bottom right hand side; original paper seal with wax and partial name of the recipient.
Article(s)
NA
Book
Jana Dambrogio and Daniel Starza Smith with the Unlocking History Research Group. Letterlocking: The Hidden History of the Letter. Cambridge and London: MIT Press, 2025.
Citation for the letter(s)
UH0890
Original
Caterina Sforza to Ludovico Sforza, Imola Ludovico Sf[irzue] (December 18, 1477). White Collection of Italian Renaissance documents, Morgan Library and Museum, MA.2691.12.
Model
MIT Libraries, Unlocking History Research Group archive, MC0760, Box 54.