[1] Unlike the German practice of sliding block breeches that required a metallic cartridge case to seal the gun's chamber against combustion gases, Škoda preferred to use an interrupted screw breech with a de Bange obturator to seal the chamber.

This lowered the rate of fire, but had the great economic advantage of allowing bagged propellant charges that didn't use heavy brass cartridge cases (copper might be in short supply in wartime).

This was a single piece of steel that was radially expanded under hydraulic pressure, a technology developed during WWI.

[2] The box trail carriage revolved on a turntable that sat on a ball race on the firing platform and was capable of 360° traverse.

[3] During the war, nine of these guns were sold to Sweden, where they were used to equip three heavy mobile coastal batteries.

The original Czech 21 cm Gr 39 (t) high-explosive shell had both nose and base fuzes and a filling of 18.8 kilograms (41 lb) of TNT.

The German equivalent, the 21 cm Gr 40, lacked the base fuze, had a copper driving band well forward on the shell and was fitted with a thin metal casing behind the driving band filled with a graphite mixture intended as a bore lubricant and to reduce wear.

The 21 cm Gr 39 Be was a Czech-designed anti-concrete shell fitted with a base fuze, a ballistic cap and the additive sleeve.