Through Hull Drain Stain

[NYClipper171]

While shopping for my first Cape Dory Typhoon I found an interesting telltale. The starboard through hull from the cockpit had a rust stain line. Not uncommon except for the direction the stain led. The stain started at the through hull and ran up toward the starboard water line. Normally a stain line such as this would lead from the hole toward the keel and down. Anyone ever seen this and what is the cause?