Abstract: Mandrel-cured, curved elastomeric hose is provided with an indexing mark that is formed prior to or during curing of the hose on the mandrel. The rigid curved mandrel has an exterior hose-bearing surface and an interior cavity. The cavity and exterior surface are connected by a small passageway or hole which is located where the index mark is to be made on the hose. A sleeve having a wall of uncured elastomeric material is mounted on the mandrel such that a portion of the sleeve covers the passageway. The mandrel having the sleeve mounted thereon is placed in an autoclave and subjected to steam pressure. The steam pressure forces elastomer material into the passageway and thereafter cures the elastomer sleeve into a hose. The pressure inside the cavity is approximately atmospheric at the introduction of the steam pressure. The cavity within the mandrel may be sealed except for the passageway or the cavity and the passageway may be vented to atmospheric pressure.