...I want to match the last 2 characters of any string (if numeric) that doesn't look like this:...

And here is your "this" explained that you don't want the last two characters to match:

/^[s][0|6]00[0-9]{2}/

    ^ Start of string

    Char class [s] matches one of the following chars: s

    Char class [0|6] matches one of the following chars: 0|6

    00 Literal `00`

    Char class [0-9] 2 times matches one of the following chars: 0-9
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Your regex matches (or doesn't match) much more than the last two characters of any string. 2teez already mentioned your data, and it would be helpful if you would show a sample along with what you'd like to exclude from it via a regex.