I recently acquired an old Peterborough #4 cedar rib canoe I'm going to start work on and noticed something curious. (for those of you who are interested the serial number, on the combing, is 2559 4). The attached pic shows what must be a support of some kind behind the stern thwart that I assumed had been added later (as other seat contraptions had) until I checked my other cedar rib and sure enough, it had the same support. But there's no indication of anything being screwed into it and I'm wondering if anyone has a canoe with one of these intact or an idea/pic of what I am assuming would be a bench or back rest of some sort that would have been used. On another note, please, please tell me that there exists a chemical or technique that will remove silicone that has been jammed into every little gap in between about 180 ribs?