Early Rookwood: http://www.justartpottery.com/rookw...-1880-cooperage-co-commercial-ware-mug/23681/ http://www.invaluable.com/auction-l...e-company-yellow-glazed-mug-2097-c-508862db3f Certainly looks probable. Just be aware that there is new Rookwood out there now since they re-opened a few years back and are making some new pieces that are similar to old time pieces.
Kard, I bought this tankard yesterday and came across your post while researching. Mine has the same logo across the front but is also marked Rookwood on the bottom.
I recently saw a piece identical to ascot's at an auction. It hammered for $130 which I though was a bit on the high end. Auctioneer said that before the rise of the internet and eBay these were thought to be scarce and once sold for $500-700 each at art pottery auctions. Very early pieces, Rookwood Pottery was founded in 1880.