It looks like you're right. The bridge is made of wood, but doesn't have the white stripes on it. The change must have happened ages ago though, because the bass has just been standing in the corner of my mate's living-room since about 1971. Also, there is a support wire connecting it to the scratchplate which is aged and rusted and appears to be original.
@hofner experts, were there occasional basses built with stripeless bridges??