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This is a spanish coast defence gun: Ordoñez 155 mm model 1885.
Numerically was the most important gun in the defence system of Havana and San Juan during the spanish-american war of 1898.
It was of an inner steel tube (since the "E" from "entubado", tubed) with wrougth iron coils ("HS" or "hierro sunchado") sourrounding it, keeping the compression of the inner tube. Initially it was built with any recoil mechanism, latter a pair of hydropneumatic cilinders were attached to the plataform. It was a dependable gun, much cheaper than Armstrong or Krupp guns, but with less range and penetration.
The gun had active service until the Spanish Civil War, and due the critical situation of Europe, until 1945 despite its obsolescence. Cheers.