Description
Technical Manual Change 1 (TM 9-1240-227-35P) for M20A1, M20A3, M20A3C, M20A3F, and M20A3G Periscopes December 1964
This Technical Manual Change 1 for TM 9-1240-227-35P covers the M20A1, M20A3, M20A3C, M20A3F, and M20A3G Periscopes and is dated 11 December 1964.
The change updates the original field- and depot-maintenance repair-parts and special-tools manual issued on 14 January 1964.
Historical Significance
The M20 series belonged to the postwar generation of U.S. armored-vehicle fire-control equipment developed from the T35 Periscope. Variants of the family served in vehicles including the M41 Walker Bulldog, M47 Patton, and M48 Patton tank families.
The basic design combined a wide-view observation channel with a magnified aiming channel and graduated reticle. Later models adapted the periscope to different mounts, reticles, vehicle layouts, and weapon-system requirements.
Armored-Vehicle and Weapon-System Applications
The M20A1 was used in M41-series 76 mm Gun Tanks and appeared in M48-series 90 mm tank fire-control arrangements. The M20A3 continued the family in later tank installations.
The M20A3G served as the gunner's periscopic sight on the M50A1 Ontos, supporting the aiming of its six 106 mm M40A1C recoilless rifles.
What This Manual Covers
Change 1 revises the maintenance terminology throughout the base manual by replacing the older third-, fourth-, and fifth-echelon designations with direct support, general support, and depot maintenance terminology.
It changes the publication title, replaces the supersession statement, and updates Section II of the repair-parts and special-tools lists. The illustrated change pages add or revise Federal Stock Numbers, descriptions, quantities, maintenance allowances, and figure or item references for covered components.
Key Features
- Publication number: TM 9-1240-227-35P, Change 1
- Change date: 11 December 1964
- Original manual date: 14 January 1964
- Maintenance scope: direct support, general support, and depot
- Models covered: M20A1, M20A3, M20A3C, M20A3F, and M20A3G
- M20A1 Federal Stock Number: 1240-344-4645
- M20A3 Federal Stock Number: 1240-546-9580
- M20A3C Federal Stock Number: 1240-692-1325
- M20A3F Federal Stock Number: 1240-707-1265
- M20A3G Federal Stock Number: 1240-886-5889
Why This Manual Matters
Change notices preserve corrections and supply information that may not appear in an unmodified copy of the original manual. This update records the Army's revised maintenance-level terminology and amended repair-parts data for the M20 periscope family.
It is a focused reference for identifying later-authorized components, understanding parts-list revisions, and assembling a more complete technical-publication set for these armored-vehicle optics.
About This Manual
Published by Headquarters, Department of the Army on 11 December 1964, this is Change 1 to TM 9-1240-227-35P, dated 14 January 1964.
The revised supersession statement identifies SM ORD 8 SNL F-235, Volume 15, dated 30 April 1957 and including Change 1 dated 23 June 1958, and SM ORD 9 SNL F-235, Volume 15, dated March 1953 and including Change 1 dated 31 December 1954. This change notice supplements the base manual rather than replacing it as a complete standalone publication.
Ideal For
This manual change is a strong fit for:
- U.S. Army technical-manual and change-notice collectors
- M41, M47, and M48 tank restorers
- M50A1 Ontos restoration and research projects
- Military optical-instrument and fire-control researchers
- Armor museums and reference libraries
Approx length 8", Approx width 10", Approx height .1", Approx weight .1lbs.
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