| 1948 |
Established Shonan Plastics Mfg. Co., Ltd. Start Plastic Molding Processing Industry |
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| 1954 |
Established Shonan Plastics Mfg. Co., Ltd. |
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| 1955 |
Established a Mold Factory |
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| 1984 |
Established Ibaraki Factory |
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| 1991 |
Established Ibaraki Yasato Factory / Started Construction Related Business |
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| 1996 |
Establish Thailand Factory / Shonan Gousei （Thailand） Co., Ltd. / Obtained Construction Business License |
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| 1998 |
Established Ibaraki Kakioka Factory |
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| 2004 |
Established SIS ENG (changed company name to SGK Co., Ltd. in November 2020) |
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