I have 3 filz helmes in the collection.....Baden, Prussian Pioneer and Prussian Infantry, all have black liners in them and brass/silver fittings. The Prussian Inf with brass fittings actually has an oil cloth liner not leather but as stated it is black. The reason for the different stitch methods between filz liners and leather helmets has to do with the visors. On leather helmets, the shell is made, then lacquered, the liner stitched on around the outside rim flesh side out. The liner is then folded down over the rim and into the interior of the shell. Finally, the visors are stitched on over the edge of the liner.
This method does not work with the filz helme because obviously, the visors are not stitched on separately they are formed with the shell when the felt is blocked into shape. The filz helme liner is stitched to the inside rim of the shell flesh side out then folded over to hide the stitches.