972Cyphersolver

Constantinople → The Hague · marked numerical code · 26 August 1799 · attempted, not solved

Van Dedem to the Burger Agent, Constantinople, 1799

Frederik Gijsbert van Dedem
fromFrederik Gijsbert van Dedem
Maarten van der Goes
toMaarten van der Goes

A despatch of the Dutch ambassador at the Porte to the Batavian Republic’s Agent of Foreign Affairs, in a code of marked number groups that has no known key and has not yet been transcribed.

Daniel Bourdeau · posted

Method: not solved · Extent: text not obtained

At a glanceNot solved · text not obtained

The letter
F.G. van Dedem tot de Gelder, ambassador at Constantinople, to the “Burger Agent” Maarten van der Goes, No. XVIII, “Duplicaat”, 26 August 1799.
Where
Nationaal Archief, The Hague, 2.01.08 (Van der Goes), inv. 346; DECODE R1895, four images. The first image is an unrelated clear page signed Schimmelpenninck.
The cipher
Two- and three-digit groups separated by points, many carrying a mark above (×, ″, a bar or a tilde) or a line below, in the style of Croiset’s marked codes. It is not the code of Van Dedem’s despatches of 1788–93.
How it was tried
Compared with the 1788–93 code and its deciphered siblings, and found different. No key for it is on DECODE.
Still open
The transcription of the two code pages and a key.

This page was split on 14 October 2026 from the entry for catalogue item 225. Van Dedem’s despatches of 1788–93 to Van de Spiegel are in another code, a different cipher with its own page: Van Dedem at Constantinople, 1788–1793.

01 The record

Heading XVIII Duplicaat, Burger Agent, dated 26 August 1799, then rows of two- and three-digit groups with marks above many of them
R1895, image 2: the heading “XVIII. Duplicaat. Burger Agent” with the date, then the code: groups such as 82. 110. 195. 340. 50. with marks over many digits. The image is photographed sideways and is shown turned. Image: Nationaal Archief, The Hague, 2.01.08 inv. 346, via DECODE R1895 (image 2, turned upright).

The despatch has four images on DECODE. The first is a clear page signed Schimmelpenninck that does not belong to it. The second opens with the heading and about eleven lines of code; the third is in clear Dutch; the fourth is more code. The groups are short, two or three digits, and many carry a mark above them or a line below. In Van Dedem’s code of 1788–93 the groups run up to 3839 and have no marks, so the 1799 despatch is in another system, probably one of the marked nomenclators that the Dutch cipher office issued in Croiset’s style.

02 What remains open

03 Sources

Notes: targets/dedem1799/. The record was examined in the joint entry, targets/dedem1788/, on 21 September 2026.