The first was a steel skullcap (known as a secret) usually worn by archers that continued to be worn into the 17th century by musketeers. It was also worn by civilians under their regular hats, including the judges at Charles I's trial. The prosecutor, John Bradshaw, feared assassination so had a special metal hat made to protect him.
The lobster-tailed pot had ear flaps, a visor that included a sliding nasal bar to protect the trooper from sword thrusts and an articulated "tail" protecting the back of a head that was said to resemble a lobster. Another common name for it was the "harquebusier's pot" as by this time the cavalry had adopted carbines.
It was invented in Germany around 1630 and saw use in the Thirty Years War where it was known as the Zischagge. Many of these European-made capelines were later imported during the English Civil War. Sometimes older helmets like the burgeonet or sallet were modified to resemble the lobster pot although these were less effective in the field.
Similar helmets were worn in the late 17th century by Polish winged hussars and Prussian cavalry, including Fredrick William's forces at the Battle of Fehrbellin (1672). The latter had a decorative fluted design and were painted black to prevent rust.