sardines in olive oil

Sardines in olive oil A shop in Lisbon exclusively sold sardines this interested me since my Norwegian mother had worked at a factory selling tinned sardines I asked if they had sardines from other country they didn't but told me in tinned bacalao they  cod fish came from Norway I noticed sardines in olive oil with the year the tin was made, began from 1905 to 2024 but the years from 1930 to 1943 were missing  I asked why, but no one knew, I think no one had noticed the gap The staff at the shop, when I told them about my mother was charmed and gave me a couple of sardine tins from 1944