Nice boat! There are only three likely builders; Ontario Canoe Co, Peterborough Canoe Co or Canadian Canoe Co. It is an early watercraft, most likely built before 1910 and my guess is that Peterborough Canoe Co is the builder.
Was it built as a rowing skiff or is it a cut-down canoe?
Both scenarios are possible. Picture #3 in Dave's second post shows what I think is screw holes from another thwart which would be in the right location for a center thwart in a model #9, 18 1/2ft cedar-rib canoe. However, a cedar-rib canoe or boat is known to open up and loosing its shape so a thwart might have been a necessity.
So, did Peterborough Canoe Co. build any cedar-rib boats?
Yes, they advertised double ended rowing skiffs in lengths from 17' to 19' although I've never seen one. Peterborough also heavily advertised at this time that they could build anything from a canoe to a steamboat..."If you cannot find what you want in our catalog, write us and we shall be glad to build you anything you may require, and furnish any information needed".
Without a thorough survey of the boat and especially the details around the transom I can't say for sure if this is a canoe that has been cut off or it was built like that. A Peterborough Canoe Co. custom made rowing skiff of this kind would be very rare and likely valuable if it could be determined and documented as being original.
Dick Persson
Buckhorn Canoe Company
Buckhorn, Ontario
http://www.buckhorncanoes.com