They seem to be factory fitted rather than a later addition, although I suppose one can never be absolutely sure considering the skill of some people in adapting models.
The screens are very badly broken and the rear window is missing. The front suspension is broken too and there are scratches on the roof and knocks here and there. The screen appears to have the two horizontal lines that I’ve only seen on the second rally car, the Sunbeam variant #340! So, all in all it’s quite a mystery and not one I expect to see solved any day soon.
And following on from the 'list' discussion earlier, no, this will not be in the list of variants!