There is a lot of references, original photos etc.. about the pre war time...mostly in polish on .pl sites
A few words about the 7TP:
7TP was a was based on the Vickers 6-ton. A Swiss Saurer engine was installed making the 7 TP the first diesel powered tank to be in production. The single turret version was armed with a modified Bofors 37 mm.It also was equipped with a Polish-made clone of the American Browning M1917 heavy machine gun. Produced with only minor modifications, it was an unlicensed copy of its predecessor and was the standard machine gun of the Polish Army.
Among the most notable differences between the original and the Polish clone were:
1. Different calibre, adapted to the Polish standard 7.92x57mm ammunition
2. Loophole iron sights replaced with V-notch sights
3. Butt handle of the weapon was lengthened for easier carriage
4. Longer barrel for greater precision and accuracy
5. Rifle lock was modified for easier exchange of used-up barrels
6. The lock was modified for easier handling
7. The mounting was adapted for anti-aircraft fire
8. Sights were adapted for AA fire as well as a handle for aiming in the air was added
7TP was also first tank quipped with rotary periscope.
Gundlach Rotary Periscope, Patented in poland in 1936, which made possible 360° vision. The periscope enabled an observer (e.g., the tank commander) to look forward or backward without moving his seat. Since it greatly increased the comfort of observer and widened the field of view, the new periscope design was used in virtually every tank built after 1940.
It was first implemented in TKS and 7TP Polish tanks. As a part of Polish-British pre-war military cooperation, the patent was sold to Vickers-Armstrong. It was produced as Vickers Tank Periscope MK.IV, and built into all British tanks (such as Crusader, Churchill, Valentine, Cromwell). After the fall of Poland, Germany, USSR and Romania captured equipment, allowing them to copy the invention. In the USSR, the Gundlach periscope was known as MK-4 and implemented in all tanks (including the T-34 and T-70). All Axis tanks and APC (including tanks of Italy, Romania, Hungary, Finland and Japan) were equipped or retro-fitted with this periscope until 1941. The technology was later transferred to the USA and implemented as the M6 periscope in all US tanks (M3/M5 Stuart, M4 Sherman and others). After the Second World War the technology was adopted thorough the whole world.