▁pair ▁of ▁ 7 - p ound er ▁guns . ▁ ▁The ▁ship ▁was ▁protected ▁with ▁comp ound ▁arm or ▁with ▁a ▁steel ▁face ▁manufact ured ▁by ▁the ▁German ▁firm ▁S iem ens ; ▁the ▁use ▁of ▁steel ▁arm or ▁was ▁a ▁new ▁development ▁in ▁naval ▁technology , ▁and ▁permitted ▁significant ▁weight ▁sav ings . ▁The ▁main ▁arm ored ▁bel t ▁was ▁ ▁thick ▁amid ships , ▁and ▁reduced ▁to ▁ ▁at ▁the ▁bow ▁and ▁stern . ▁Below ▁the ▁main ▁bel t ▁was ▁a ▁stra ke ▁of ▁arm or ▁that ▁was ▁ ▁thick ▁amid ships ▁and ▁ ▁on ▁either ▁end ▁of ▁the ▁ship . ▁The ▁central ▁battery ▁was ▁protected ▁by ▁ 8   in ▁of ▁arm or ▁plate ▁in ▁the ▁lower ▁stra ke , ▁and ▁ 6   in ▁of ▁arm or ▁in ▁the ▁upper ▁stra ke . ▁At op ▁the ▁central ▁battery , ▁the ▁arm ored ▁deck ▁was ▁ ▁thick , ▁while ▁the ▁deck ▁fore ▁and ▁a ft ▁of ▁the ▁battery ▁was ▁ ▁thick . ▁The ▁con ning ▁tower ▁also ▁had ▁ 8   in ▁thick ▁sides . ▁ ▁Service ▁history ▁ ▁In ▁ 1 8 7 8 , ▁Argentina ▁made ▁in qui ries ▁in ▁Britain ▁to ▁buy ▁a ▁new , ▁ocean - going ▁capital ▁ship ▁for ▁its ▁n avy , ▁which ▁to ▁that ▁point , ▁had ▁consisted ▁of ▁only ▁coast al ▁and ▁river ine ▁forces , ▁centered ▁on ▁the ▁two ▁small ▁s . ▁Al mir ante ▁Brown , ▁the ▁first ▁large ▁iron cl ad ▁of ▁the ▁Argent ine ▁Navy , ▁was