Sterlingworth Company pin gun

[Jawjadawg]

I saw one of these today. At first glance I thought it was a Parker, and couldn't hardly believe it when I saw that it was one of the early Fox pin guns, roll stamped Philly. The left barrel appears to have several straight line "ruts" in the bore that travel from the chamber down the majority of the barrel. Not very deep, but also easy to see. These look like someone shot steel shot down the barrel, and perhaps after several shots when the barrels scorching hot, the steel shot was able to sink in to the metal to leave what I might also describe as gutters in the bore.

Has anyone else seen this, and am I correct about the cause? Makes me think the gun might not be safe to shoot.