Pakled: the hard-wiring is simple, but probably not useful for a prop.

The line smoothPolys 1  is created by default in each figure or prop you save, and you just change it to smoothPolys 0 if you want this body part to be unsmoothed. 

Actually you don't even need to edit this.  Set the polygon smoothing Off in the body part's Properties before saving, and Poser will make it 0 when it creates the file.   But I find that the change usually needs to be made after creating the file, because the bulges and breaks aren't always obvious until I use the figure in a render or two.

This probably won't be useful for the OP here, since a prop has only one part, and it seems that the prop needs smoothing in some areas but not others.  We still don't have a picture, so that's a guess.

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