Description
Technical Manual (TM 9-1240-227-34) for M20/T35, M20A1, M20A2, M20A3, M20A3C, and M20A3F Periscopes November 1960
This Technical Manual TM 9-1240-227-34 covers the M20/T35, M20A1, M20A2, M20A3, M20A3C, and M20A3F Periscopes and is dated November 1960.
The publication is a field-maintenance reference for the M20 family of armored-vehicle periscopes used for observation and direct-fire sighting.
Historical Significance
The T35 Periscope was standardized as the M20 during the development of a new generation of postwar U.S. armored-vehicle fire-control equipment. M20-series instruments were employed in light and medium tanks including the M41 Walker Bulldog, M47 Patton, and M48 Patton families.
The basic M20 combined a wide-view one-power observation system with a six-power optical system and graduated reticle for aiming at distant targets. Later variants adapted this established periscopic sight design to different mounts, reticles, vehicle arrangements, and fire-control requirements.
Armored-Vehicle and Fire-Control Applications
On the M41 and M41A1 76 mm Gun Tanks, M20 or M20A1 periscopes served both the gunner and commander. The T35/M20 was also part of the M47's gunnery equipment, while M20A1 and M20A3 variants were incorporated into M48-series 90 mm tank fire-control systems.
The manual also includes the M20A3C, a periscopic sight used by the gunner of the M50A1 Ontos to lay its battery of 106 mm recoilless rifles. These varied applications show why maintenance documentation covering the complete M20 family is useful beyond a single vehicle model.
What This Manual Covers
TM 9-1240-227-34 provides field-maintenance information for six related periscope configurations. It supports maintenance personnel working beyond routine operator care by documenting the construction, servicing, repair, adjustment, and testing of the covered optical instruments.
By placing the M20/T35 and five later variants in one publication, the manual helps identify shared assemblies and model-specific differences across this important family of Cold War armored-vehicle sights.
Key Features
- Official publication number: TM 9-1240-227-34
- Publication date: November 1960
- Manual type: field maintenance manual
- Models covered: M20/T35, M20A1, M20A2, M20A3, M20A3C, and M20A3F
- Equipment type: armored-vehicle observation and direct-fire periscopes
- Documented applications include M41, M47, and M48 tanks and the M50A1 Ontos
Why This Manual Matters
The M20 series was closely integrated with the gunner's station, periscope mount, weapon elevation system, and other fire-control components. This manual preserves the Army terminology and maintenance practices needed to understand those relationships and distinguish similar-looking variants.
It is particularly useful when identifying loose optical assemblies, researching a vehicle's correct sighting equipment, or supporting the restoration and interpretation of early Cold War armored vehicles.
About This Manual
Published by Headquarters, Department of the Army in November 1960, TM 9-1240-227-34 is dedicated to field maintenance of the M20 periscope family.
The publication covers the standardized M20 and its earlier T35 designation together with the M20A1, M20A2, M20A3, M20A3C, and M20A3F variants. It is a maintenance publication rather than a vehicle operator's manual or repair-parts catalog.
Ideal For
This manual is a strong fit for:
- U.S. Army technical-manual collectors
- M41 Walker Bulldog, M47 Patton, and M48 Patton 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 .2", Approx weight .2lbs.
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