T-26M38 equipped with radio transmitter. The vehicle has a conical turret with welded gun mask, battle searchlights, a hatch for P-40 machine-gun ring, commanders "PTK" periscope and a machine-gun in a rear recess 
Photo: shows the T-26 tank (year 1938 production series) during testing. NIIBT polygon summer 1938. (the photo from M.Svirin's collection) 
Tank T-26-1 mod. 1940, equipped with radio transmitter. It has a sloping hull below the turret and a conical turret with punched gun mask, commander’s "PTK" periscope and whip antenna.
Photo: The T-26-1 tank on the road to battle. Western Front, December 1941.
Finnish version of T-26 tank - a conic turret of T-26-1 line tank is mounted on the hull of OT-133 with spherical mount for DT machine-gun. 
Photo: Finnish version of T-26 tank - a conical turret of line tank is mounted on the hull of OT-130 with spherical mount for DT machine-gun. Autumn, 1942. 
Slit of T-26-1 (mod. 1940) 
Board gear (behind armored shield);
Bulkhead between Engine and Combat sections;
Armored louvre over oil radiator;
45mm gun 20K;
Hinged driver protection shield;
Composition of T-26 mod. 1939 
Gun layer’s hatch;
Commander's hatch with machine-gun ring;
Sloping hull below the turret;
Gasoline & oil tank fillers access hatch;
Magneto and generator hatch;
Engine access hatch;
Hinged frontal cover;
Composition of conic turret 
Racking for 5 shells;
Right sight device;
Radio receiver set;
56-U322B machine-gun mount;
Armour plating diagramme of a T-26 with conical turret 
Machine-gun ring mounting [?]
M. Kolomiets, M. Svirin,"T-26 Legkiy Tank"
Frontovaya Illystratsiya, No. 1, 2003
Pavlov I.V. Pavlov M.V. "Sovetskiye Tanki I Samokhodno-Artilleriyskiye Ustanovki 1939-1945" M. 1996.