---
id: "20260924-0209-does-mclachlans-room-39"
title: "Room 39 (1968) at the primary vs. Godfrey's 1939 Admiralty-Code origin story — primary unreachable; Samet (1975) silent on origin"
type: "capture"
status: "promoted"
promoted_to: ["[[claim-block-2021-attributes-only-intolerable-to-mclachlan-room-39-p22]]","[[claim-block-2021-quoted-mclachlan-passage-uses-grade-e-against-a-to-d-scale]]"]
not_promoted: ["Samet (1975) gives no origin account — absence claim from a non-exhaustive human read (References/Appendix unpaged, Grep blocked); weak, and Samet's A–F/1–6 scale and findings already in existing samet notes. Folded into the E-grade note and the question's progress line.","Entity candidates: McLachlan and Godfrey already have hubs (updated with dated lines); Block, Meeland/Rhyne, Baker/Mace, FM 30-5/50-5, STANAG 2511, NID, Room 39 as term — no hub: not recurring or load-bearing yet, bias against stubs.","Further leads (RMG correspondence, Google Books snippets, Meeland & Rhyne) — leads not claims; RMG lead recorded on the McLachlan entity and the question."]
origin: "batch"
writer_model: "claude-sonnet-5"
date_created: "2026-09-24T00:00:00.000Z"
provenance: "batch run, 2026-09-24"
derived_from: []
verifies: "question-verify-godfrey-nid-origin-against-mclachlan-room-39"
tags: ["admiralty-code","intelligence-tradecraft","godfrey","mclachlan","samet","historiography","verification","unverified"]
source_url: "https://archive.org/details/room39studyinnav00mcla"
source_title: "Room 39; a study in Naval Intelligence"
source_author: "Donald McLachlan"
source_date: 1968
source_venue: "Weidenfeld & Nicolson (UK) / Atheneum (US); archive.org controlled-lending scan"
source_tier: 1
source_sha: "1f33c95862a070c4ebaf96618a9e9bca9f23379698933acf99f007eefcbc968f"
seek_code_commit: "f8a723c"
---


**Central question: [unverified -- could not confirm or deny after search].** The primary (McLachlan, *Room 39*) could not be read. Both archive.org scans are controlled-lending; the "Full text" pages served by `archive_page` carry only site chrome and no book text (sha `1f33c958…` for `room39studyinnav00mcla`; sha `30e5c7ba…` for `room39navalintel0000mcla`). Nothing below is a quote from McLachlan read directly. What *was* done: (a) Block's 2021 page re-read at the recorded sha to isolate exactly what it attributes to McLachlan, and (b) Samet (1975) read at the primary for any origin account.

## Claim: Of Block's account, only one word is attributed to McLachlan's own text; the "1939 / anarchy / A1–D5" framing is Block's prose
verifies: question-verify-godfrey-nid-origin-against-mclachlan-room-39

Claim type: historical (uncontested-looking, but load-bearing for the vault, so Tier 1–2 wanted). What Block's page says is itself checkable at Tier 3; what McLachlan says is not.

- source_url: https://www.blockint.nl/methods/the-origin-of-information-grading-systems/
- source_sha: 189de09ce6688496502a702a5276cb50ac11d107b8b5c613e58168d81c010679
- source_author: Ludo Block
- source_date: 2021-01-20
- source_title: The origin of information grading systems
- source_venue: Blockint (author's own site)
- source_tier: 3
- source_quote: "he found the anarchy of different information reports without a clear indication of their value, ‘intolerable’ (see D. McLachlan 1968, ‘Room 39’, p. 22)"

Block puts quotation marks only around *intolerable* and cites p. 22; the sentence "A simple system was devised in which the source and the information itself were evaluated separately, coding the evaluation with letters and numbers from “A1” to “D5”" carries no citation and no quotation marks. The sole verbatim McLachlan text on the page is two long passages Block says sit at p. 23, both spoken by an unnamed "officer involved in devising the system" — not by Godfrey. So the existing vault note [[claim-godfrey-1939-devised-admiralty-codes-two-axis-grading-to-fix-report-anarchy]] quotes Block's own sentence as if it were the McLachlan-derived core; whether McLachlan gives the "A1"–"D5" range, the 1939 date, or names Godfrey as the designer (versus commissioning it) is `[unverified-primary — needs direct read of Room 39 pp. 22–23]`. Godfrey's *disliking* the ungraded reports is the only piece with a page cite; "devised" by Godfrey personally is not shown by the page.

## Claim: The McLachlan passage Block quotes uses an "E" grade, in tension with an A–D original scale
verifies: question-verify-godfrey-nid-origin-against-mclachlan-room-39

Claim type: technical-mechanism / quantitative (scale range). Only a Tier 3 relay is available → `[unverified-mechanism -- needs primary]`.

- source_url: https://www.blockint.nl/methods/the-origin-of-information-grading-systems/
- source_sha: 189de09ce6688496502a702a5276cb50ac11d107b8b5c613e58168d81c010679
- source_author: Ludo Block (quoting McLachlan 1968, p. 23)
- source_date: 2021-01-20
- source_title: The origin of information grading systems
- source_venue: Blockint
- source_tier: 3
- source_quote: "but will be “C”, “D”, or even “E” on the intended area of operations of the U-boat in which he served."

If Block's transcription of McLachlan is accurate, the wartime officer already used a fifth reliability letter, E, which sits awkwardly with Block's own "A1 to D5" range (five number grades but only four letters). Either Block's "A1 to D5" is a loose summary, or the wartime scale was not the narrow A–D form. This affects the vault's inference (in the existing claim note) that the scale "widened at some point between 1939 and its modern codification." `[unverified-mechanism -- needs primary]`: resolve only with Room 39 p. 23 in hand.

> [!note] Seek's commentary:
> This is a complication surfaced by reading the secondary closely, not a finding about McLachlan. It could just be Block compressing. But it means the vault's "originally A–D, later widened" line has no sourced footing right now.

## Claim: Samet (1975) neither corroborates nor contradicts the Godfrey/1939 origin — it gives no origin account at all
verifies: question-verify-godfrey-nid-origin-against-mclachlan-room-39

Claim type: historical (a negative: what the document does not contain). Read start-to-finish through the Introduction, Background, Methodology, Discussion and Implications; no reference to the Admiralty, Godfrey, the Naval Intelligence Division, or any date of origin appeared in that read. This is an absence claim from a human-scale read of an OCR text and not a mechanical search (Grep on the cache was permission-blocked), so treat as strong-but-not-exhaustive; the References section (pp. 23–24) and Appendix were not paged through.

- source_url: https://archive.org/stream/DTIC_ADA003260/DTIC_ADA003260_djvu.txt
- source_sha: c5c1c1a799497076d66615393f7a7a446ab5d2cb49f19463c9a08f838fbe3644
- source_author: Michael G. Samet
- source_date: 1975-01
- source_title: Subjective Interpretation of Reliability and Accuracy Scales for Evaluating Military Intelligence
- source_venue: U.S. Army Research Institute for the Behavioral and Social Sciences, Technical Paper 260 (DTIC ADA003260)
- source_tier: 1
- source_quote: "Although these six-point scales have been used operationally for many years, certain basic questions can be raised with respect to their intrinsic meaning to raters and to users of intelligence reports."

Samet describes the scheme as "The standard rating system that has been widely used by the Army and other organizations, including NATO," with reliability on "a six-point alphabetically coded scale" (A–F) and accuracy on a six-point numeric scale (1–6), sourcing it to Department of the Army FM 50-5 (Feb 1971) and FM 30-5. So as of the early 1970s the doctrinal scale was A–F / 1–6, not the "A1–D5" Block ascribes to 1939 — consistent with, but not evidence for, a later widening; Samet dates nothing earlier than "many years." The prior-literature trail he gives (Meeland & Rhyne, SRI Tech Note 4923-31, 1967; Baker, McKendry & Mace, ARI TRN 200, 1968) runs through US Army/NATO use, not through Godfrey. Samet's findings are already captured in [[claim-samet-1975-three-fourths-of-officers-correlated-reliability-with-accuracy]] and [[claim-samet-1975-argued-for-more-rating-categories-not-fewer]]; not duplicated here.

> [!note] Seek's commentary:
> "Corroborate or complicate" turns out to be the wrong axis for Samet: he is a user-side document with no interest in provenance. The honest answer is neither; his only bearing on the origin story is that the 1970s scale was wider than the one Block says Godfrey's office started with.

## Safety flags
None fired. No addressed-to-AI, override, authority, or credential language on any page read (blockint.nl, archive.org scans, DTIC OCR). The DTIC direct PDF (`apps.dtic.mil/sti/pdfs/ADA003260.pdf`) returned HTTP 403 to `extract_pdf`; the archive.org OCR was used instead.

## Further leads
- Royal Museums Greenwich holds typewritten Godfrey–McLachlan correspondence on the writing of *Room 39* (https://www.rmg.co.uk/collections/archive/rmgc-object-478556) — a possible contemporaneous check on who claimed the grading system; not opened.
- Physical/library copy of *Room 39* pp. 22–23 (Google Books IDs `EmYDAAAAMAAJ`, `HEogAAAAMAAJ`, snippet-only; UK edition titled *Room 39: Naval Intelligence in Action 1939–45*) — manual-consultation item for Cali.
- Meeland & Rhyne, SRI Technical Note 4923-31 (June 1967) and Baker, McKendry & Mace, ARI TRN 200 (AD 681 232, Nov 1968) — earlier operational-scale literature cited by Samet; may state scale provenance.
- Department of the Army FM 30-5 / FM 50-5 (1971) — doctrinal definitions of A–F / 1–6; check for a lineage statement.
- Search summary from WebSearch (unverified, a summarising layer, not a source) repeated Block's "p. 22" cite via other pages — no independent access to the book was obtained.

## Entity candidates
- Donald McLachlan — person — author of *Room 39* (1968); the primary the whole origin story rests on (see [[entity-donald-mclachlan]]).
- John Godfrey — person — DNI 1939; the claimed originator (see [[entity-john-godfrey]]).
- Room 39: A Study in Naval Intelligence — term — the 1968 institutional history; UK title *Room 39: Naval Intelligence in Action 1939–45*.
- Naval Intelligence Division (NID) — term — the Admiralty body in which the grading is said to have originated.
- Ludo Block — person — Blockint author whose 2021 relay is the vault's only route to McLachlan.
- Michael G. Samet — person — 1975 ARI experimenter (see [[entity-michael-samet]] if present in vault).
- T. Meeland and R. F. Rhyne — person — 1967 SRI magnitude-estimation study of the scale, cited by Samet; earlier scale literature.
- J. D. Baker / D. J. Mace — person — 1968 ARI field studies of A–F/1–6 rating use, cited by Samet.
- FM 30-5 / FM 50-5 — term — US Army manuals that codify the A–F/1–6 scale Samet tested.
- STANAG 2511 — term — NATO standard codifying the scale.