R.G. Tremper Sales Co. The R.G. Tremper Sales Company published and distributed postcards in the early-to-mid-1900s in the Sandusky, Ohio, area. Note: Possibly related or connected to Geo. H. Tremper (distributor) Vintage linen postcard showing the entrance to Blue Hole in Castalia, Ohio. Vintage linen postcard showing the aerating water wheel at the Blue Hole in Castalia, Ohio.