Description
T-42 Periscope
The T-42 Periscope, standardized as Sight, Periscope M25 (T42), was the commander's anti-aircraft machine-gun sight principally documented for the M48A1 90 mm gun tank. Installed in the M104 periscope mount through the roof of the M1 commander's cupola, it let the commander aim the cupola-mounted M2HB .50-caliber machine gun while remaining under armor.
The M48A1 equipment sheet identifies the T42 as the commander's AA MG sight and separately lists the M20, M20A1, or M20A2 as the gunner's direct-sight periscope for the 90 mm main gun. The T-42 Periscope is therefore a cupola machine-gun sight, not the tank's main-gun periscope.
Historical Significance
The T-42 Periscope belongs to the early Cold War development of the M48 Patton series. Its protected sighting arrangement supported the M48A1 commander's cupola, where the .50-caliber machine gun could be aimed from inside the armored cupola.
Army data standardized the sight as the M25 (T42) and assigned Federal Stock Number 1240-344-4675. TM 9-500 documents the M25 and the later M28 (T46) as separate sight models.
M25 (T42) and M28 (T46)
The M25 (T42) and M28 (T46) are different periscope sights. TM 9-500 lists the M25 (T42) with the M48A1 fire-control equipment and identifies the M28 (T46) separately for the M48A2 and M48A2C.
This distinction is important for accurate identification. The offered T-42 Periscope should not be cataloged as an M28 or T46 sight.
What This Item Is and Does
The T-42 Periscope is a monocular sight for the cupola-mounted M2HB machine gun. Its eyepiece remained stationary relative to the tank while an internal body prism followed the weapon's elevation. A quick-release link connected the gun installation to the sight's side mechanism, and tape-connected pulleys transmitted that movement to the prism.
Army data lists 1.27-power magnification, a 30-degree field of view, and line-of-sight movement from 15 degrees depression to 60 degrees elevation. The design was sealed against moisture and filled with dry nitrogen.
Key Features
- U.S. military T-42 Periscope
- Standardized nomenclature: Sight, Periscope M25 (T42)
- Federal Stock Number 1240-344-4675
- Principal documented application: M48A1 90 mm gun tank
- Installed through the M1 commander's cupola with the M104 periscope mount
- Sight for the cupola-mounted M2HB .50-caliber machine gun
- 1.27-power magnification with 30-degree field of view
- Line-of-sight movement from 15 degrees depression to 60 degrees elevation
- Fixed eyepiece with mechanically linked moving body prism
- Identification plate located on the rear of the sight
Why This Item Matters
The T-42 Periscope represents the commander's protected machine-gun sighting system used during the early M48A1 period. Its mechanical linkage and moving-prism design show how the cupola weapon's elevation was transferred to an optical sight while the eyepiece remained fixed.
Its documented M25 and T42 designations make it useful for M48A1 restoration research, armored-vehicle displays, military-optics collections, and technical study.
About This Item
The offered item is a loose T-42 Periscope, standardized as Sight, Periscope M25 (T42) and documented under FSN 1240-344-4675. Its principal documented application is the M1 commander's cupola of the M48A1 Patton tank, where it served as the sight for the cupola-mounted M2HB .50-caliber machine gun.
Army specifications give a maximum length of 5.5 inches without the link assembly, a maximum width of 6 inches, a height of 14.25 inches, and a weight of 7.81 pounds without the link assembly.
Ideal For
This item is a strong fit for:
- M48A1 Patton tank collections and restoration research
- M1 commander's cupola displays
- U.S. military optics collections
- Early Cold War armor exhibits
- Museum and educational reference collections
- Historic fire-control system study
- Film and prop department reference
Approx length 5.5", Approx width 6", Approx height 14.25", Approx weight 7.81 lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item's general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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