Engine Number identification

Hi all. I am in Australia and have purchased a 1980 Series iii 109 HardTop. It has a 5 bearing diesel however the engine number is not your typical number. It is S11J00388C. From my understanding the S could indicate that this is a replacement engine and the 11J is a military spec engine from a 90 or 110 series. Can anyone confirm (or deny this)?

Take a look at

Thanks. That's where I've been able to this information but was wondering if there was anything more.

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