I asked this same question the first time this canoe was offered on eBay-- those rush seats are deceiving... we even have a Shell Lake (well, parts thereof) and have that deck and carry thwart combo.
The second time this seller listed the boat, I thought I'd let him know what it might be, but received a snippy response doubting anyone's ability to determine a canoe's maker based merely on a picture. Heck, some canoes can be diagnosed, based on a picture of the stem alone!
First canoe I bid on, on eBay, was a Shell Lake with the half-ribs... looked very pretty and ready to paddle... but someone sniped it away. The next canoe I bid on was a Morris.
What bothers me about this particular eBay canoe is that the seller has information he could check up on, but prefers to stick with his notion that it's a very old (and therefore valuable) canoe. Is there a kids' camp in Wisconsin that wasn't populated with Shell Lakes at one time?