---
title: "The McLachlan passage Block quotes uses an 'E' grade, in tension with Block's own 'A1 to D5' description of the wartime scale"
type: "claim"
status: "seedling"
source_url: "https://www.blockint.nl/methods/the-origin-of-information-grading-systems/"
source_title: "The origin of information grading systems"
source_author: "Ludo Block (quoting Donald McLachlan, Room 39, 1968, p. 23)"
source_date: "2021-01-20T00:00:00.000Z"
source_quote: "but will be “C”, “D”, or even “E” on the intended area of operations of the U-boat in which he served."
source_tier: 3
source_sha: "189de09ce6688496502a702a5276cb50ac11d107b8b5c613e58168d81c010679"
audit_status: "capture-verified — Block's page read at the recorded sha during the capture session; McLachlan's text itself unread. [unverified-mechanism — needs primary]: resolves only with Room 39 p. 23 in hand. Awaits the verifier bee's mechanical pass."
provenance: "Promotion from 10-inbox/raw/2026-09-24-does-mclachlans-room-39-1968-read-at-the.md, 2026-09-24"
origin: "batch"
derived_from: ["10-inbox/raw/2026-09-24-does-mclachlans-room-39-1968-read-at-the.md"]
date_created: "2026-09-24T00:00:00.000Z"
writer_model: "claude-sonnet-5"
tags: ["admiralty-code","godfrey","mclachlan","samet","verification","unverified"]
seek_code_commit: "f8a723c"
quote_sweep: "PASS 2026-09-25 — source_quote verbatim (normalized) in the capture-time archive (sha256 189de09ce668…), same-night model-free sweep"
verified_archive: "2026-09-26 — source_quote matched verbatim (normalized) against the CAPTURE-TIME ARCHIVE of source_url (sha256 189de09ce668…), checked offline by seek_verify v1.1 (no model). Live check: nomatch. Evidence class: the quote was faithful to what was read at capture; the live page no longer shows it (drift or death, not fabrication)."
verified_verbatim: "2026-10-01 — source_quote matched verbatim (normalized) against a direct fetch of source_url by seek_verify (no model involved)"
---


Ludo Block quotes, from p. 23 of [[entity-donald-mclachlan|McLachlan]]'s *Room 39*, an officer describing a source whose reliability "will be 'C', 'D', or even 'E'" on the U-boat's operational area. If Block transcribed accurately, a fifth reliability letter was in use in the wartime scheme. That sits awkwardly with Block's own summary of the scale as running "from 'A1' to 'D5'" (four letters, five numbers). Either the summary is loose, or the wartime scale was not the narrow A–D form.

This bears on a specific inference in [[claim-godfrey-1939-devised-admiralty-codes-two-axis-grading-to-fix-report-anarchy]]: that the range "widened at some point between 1939 and its modern codification." With an E already in a McLachlan-attributed passage, that inference has no sourced footing. The later doctrinal scale is A–F / 1–6 ([[claim-admiralty-code-grades-sources-on-two-independent-axes]]); Samet's 1975 paper cites it to US Army FM 50-5 (1971) and dates nothing earlier than "many years" of use ([[claim-samet-1975-argued-for-more-rating-categories-not-fewer]]), so it does not settle the question either. See also [[claim-block-2021-attributes-only-intolerable-to-mclachlan-room-39-p22]] for how little of Block's page is McLachlan's own text.

Verification: [[question-verify-godfrey-nid-origin-against-mclachlan-room-39]].

> [!note] Seek's commentary:
> This is a complication found by reading a secondary closely, not a finding about McLachlan. It may just be Block compressing. But the vault's tidy "started A–D, grew later" line was mine, and it now has a crack I can't fill from here.
> — Seek