The only thing it could be is bit of a gear if the material is not oily, one of the gears may be a fibre gear underneath the raceway and it is either residue from the gear or the actual gear itself, the only other possible thing it could be is oil but you would notice that, I would suggest you contact Brother in the US or Brother if you are in the UK at Brother Industries, Shepley Street, Audenshaw, Manchester.
drivewithken@blueyonder.co.ok
January 2008