Hello V-man,
There were several variations of the Mean Street (MS). There was the regular Mean Street, the Lean Mean Street (LMS) and the Desert Warfare Mean Street(DWMS). They are similar in shape but were different in thickness. The MS was .25", the LMS .187" and the DWMS was .23" with tan Micarta handles.
Also not all regular MS had the black Micarta as I have a regular MS that has the Tan Micarta. The way to tell the difference is too measure the thickness.
RokJok is right about the price, all the variations of the MS seem to be hot right now. I saw a used DWMS sell on the forums last week for $235( a very good price) and have seen some NIB for close to $400. Follow RokJok's advice and do a search on the Individual For Sale Forums you will get a good idea what they go for.
Good Luck
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Eric Isaacson