{
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  "endpoint": "timeline",
  "stock_code": "8334",
  "company_name": "群馬銀行",
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  "updated": "2026-09-05",
  "license": "© 2026 Yutaka Sugiura. All rights reserved.",
  "attribution": "The社史 (the-shashi.com) — https://the-shashi.com/tse/8334/",
  "source": {
    "primary": [
      "有価証券報告書",
      "統合報告書"
    ],
    "extraction": "有価証券報告書の沿革を基礎に、社史・報道で補完",
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      "date": "1878",
      "importance": 2,
      "event": "第三十九国立銀行を設立",
      "source": "統合報告書"
    },
    {
      "date": "1898",
      "importance": 1,
      "event": "三十九銀行に商号変更",
      "source": "統合報告書"
    },
    {
      "date": "1932/9",
      "importance": 2,
      "event": "群馬県金融統制要項に基づき群馬県金融を設立",
      "source": "有価証券報告書"
    },
    {
      "date": "1932/10",
      "importance": 2,
      "event": "群馬大同銀行に商号変更",
      "source": "有価証券報告書"
    },
    {
      "date": "1932/11",
      "importance": 3,
      "event": "旧群馬銀行と上州銀行を吸収合併",
      "source": "有価証券報告書"
    },
    {
      "date": "1945",
      "importance": 2,
      "event": "前橋空襲により本社が焼失",
      "source": "統合報告書"
    },
    {
      "date": "1947",
      "importance": 1,
      "event": "本庄支店を開設",
      "source": "統合報告書"
    },
    {
      "date": "1952",
      "importance": 1,
      "event": "本社ビルが竣工",
      "source": "統合報告書"
    },
    {
      "date": "1955/1",
      "importance": 2,
      "event": "群馬銀行に商号変更",
      "source": "有価証券報告書"
    },
    {
      "date": "1961/4",
      "importance": 1,
      "event": "外国為替業務の取扱を開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1964",
      "importance": 2,
      "event": "群馬県の指定金融機関に指定",
      "source": "統合報告書"
    },
    {
      "date": "1969/4",
      "importance": 1,
      "event": "東京証券取引所市場第二部に上場",
      "source": "有価証券報告書"
    },
    {
      "date": "1970/2",
      "importance": 1,
      "event": "東京証券取引所市場第一部に指定替え",
      "source": "有価証券報告書"
    },
    {
      "date": "1972/4",
      "importance": 1,
      "event": "新本社ビルが竣工",
      "source": "有価証券報告書"
    },
    {
      "date": "1972/11",
      "importance": 2,
      "event": "総合オンラインシステムが稼動",
      "source": "有価証券報告書"
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    {
      "date": "1973/10",
      "importance": 1,
      "event": "群馬総合リースを設立",
      "source": "有価証券報告書"
    },
    {
      "date": "1983/4",
      "importance": 1,
      "event": "公共債の窓口販売業務の取扱を開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1984/6",
      "importance": 1,
      "event": "債券ディーリング業務を開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1988/4",
      "importance": 2,
      "event": "ニューヨーク支店を開設",
      "source": "有価証券報告書"
    },
    {
      "date": "1992",
      "importance": 1,
      "event": "企業理念とシンボルマークを制定",
      "source": "統合報告書"
    },
    {
      "date": "1993",
      "importance": 1,
      "event": "香港支店を開設",
      "source": "統合報告書"
    },
    {
      "date": "1994/1",
      "importance": 1,
      "event": "信託業務の取扱を開始",
      "source": "有価証券報告書"
    },
    {
      "date": "1998/12",
      "importance": 2,
      "event": "証券投資信託の窓口販売を開始",
      "source": "有価証券報告書"
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    {
      "date": "2001/4",
      "importance": 1,
      "event": "保険商品の窓口販売を開始",
      "source": "有価証券報告書"
    },
    {
      "date": "2005/8",
      "importance": 1,
      "event": "証券仲介業務の取扱を開始",
      "source": "有価証券報告書"
    },
    {
      "date": "2011",
      "importance": 1,
      "event": "上海駐在員事務所を開設",
      "source": "統合報告書"
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    {
      "date": "2016/2",
      "importance": 1,
      "event": "ぐんぎん証券を設立",
      "source": "有価証券報告書"
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    {
      "date": "2020",
      "importance": 2,
      "event": "TSUBASAアライアンスに参加",
      "source": "統合報告書"
    },
    {
      "date": "2021",
      "importance": 3,
      "event": "第四北越銀行と業務提携",
      "source": "統合報告書"
    },
    {
      "date": "2022",
      "importance": 1,
      "event": "創立90周年",
      "source": "統合報告書"
    },
    {
      "date": "2022/4",
      "importance": 1,
      "event": "プライム市場に移行",
      "source": "有価証券報告書"
    },
    {
      "date": "2025/4",
      "importance": 3,
      "event": "第四北越フィナンシャルグループと経営統合の基本合意書を締結",
      "source": "有価証券報告書"
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    {
      "date": "2026/3",
      "importance": 3,
      "event": "第四北越フィナンシャルグループと株式交換契約を締結",
      "source": "有価証券報告書"
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    {
      "date": "2027",
      "importance": 2,
      "event": "共同持株会社 群馬新潟フィナンシャルグループを設立予定",
      "source": "統合報告書"
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}